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8E6 Internet Security Solutions
Home Network Security
given elsewhere, so we won't cover it in detail in this document.
However, it is important to know a few things about IP in order to
understand how to secure your computer. Here we’ll cover IP addresses,
static vs. dynamic addressing, NAT, and TCP and UDP Ports.
- Computer security
- What is computer security?
Computer security is the process of preventing and detecting
unauthorized use of your computer. Prevention measures help you to
stop unauthorized users (also known as "intruders") from accessing any
part of your computer system. Detection helps you to determine whether
or not someone attempted to break into your system, if they were
successful, and what they may have done.
- Why should I care about computer security?
We use computers for everything from banking and investing to
shopping and communicating with others through email or chat
programs. Although you may not consider your communications "top
secret," you probably do not want strangers reading your email, using
your computer to attack other systems, sending forged email from your
computer, or examining personal information stored on your computer
(such as financial statements).
- Who would want to break into my computer at home?
Intruders (also referred to as hackers, attackers, or crackers) may
not care about your identity. Often they want to gain control of your
computer so they can use it to launch attacks on other computer
systems.
Having control of your computer gives them the ability to hide
their true location as they launch attacks, often against high-profile
computer systems such as government or financial systems. Even if you
have a computer connected to the Internet only to play the latest
games or to send email to friends and family, your computer may be a
target.
Intruders may be able to watch all your actions on the computer, or
cause damage to your computer by reformatting your hard drive or
changing your data.
- How easy is it to break into my computer?
Unfortunately, intruders are always discovering new vulnerabilities
(informally called "holes") to exploit in computer software. The
complexity of software makes it increasingly difficult to thoroughly
test the security of computer systems.
When holes are discovered, computer vendors will usually develop
patches to address the problem(s). However, it is up to you, the user,
to obtain and install the patches, or correctly configure the software
to operate more securely. Most of the incident reports of computer
break-ins received at the 8e6/CC could have been prevented if system
administrators and users kept their computers up-to-date with patches
and security fixes.
Also, some software applications have default settings that allow
other users to access your computer unless you change the settings to
be more secure. Examples include chat programs that let outsiders
execute commands on your computer or web browsers that could allow
someone to place harmful programs on your computer that run when you
click on them.
- Technology
This section provides a basic introduction to the technologies that
underlie the Internet. It was written with the novice end-user in mind
and is not intended to be a comprehensive survey of all Internet-based
technologies. Subsections provide a short overview of each topic. This
section is a basic primer on the relevant technologies. For those who
desire a deeper understanding of the concepts covered here, we include
links to additional information.
- What does broadband mean?
"Broadband" is the general term used to refer to high-speed network
connections. In this context, Internet connections via cable
modem and Digital Subscriber Line (DSL) are frequently referred to as
broadband Internet connections. "Bandwidth" is the term used to
describe the relative speed of a network connection -- for example,
most current dial-up modems can support a bandwidth of 56 kbps
(thousand bits per second). There is no set bandwidth threshold
required for a connection to be referred to as "broadband", but it is
typical for connections in excess of 1 Megabit per second (Mbps) to be
so named.
- What is cable modem access?
A cable modem allows a single computer (or network of computers) to
connect to the Internet via the cable TV network. The cable modem
usually has an Ethernet LAN (Local Area Network) connection to the
computer, and is capable of speeds in excess of 5 Mbps.
Typical speeds tend to be lower than the maximum, however, since
cable providers turn entire neighborhoods into LANs which share the
same bandwidth. Because of this "shared-medium" topology, cable
modem users may experience somewhat slower network access during
periods of peak demand, and may be more susceptible to risks such as
packet sniffing and unprotected windows shares than users with other
types of connectivity. (See the "Computer
security risks to home users" section of this document.)
- What is DSL access?
Digital Subscriber Line (DSL) Internet connectivity, unlike cable
modem-based service, provides the user with dedicated bandwidth.
However, the maximum bandwidth available to DSL users is usually lower
than the maximum cable modem rate because of differences in their
respective network technologies. Also, the "dedicated bandwidth" is
only dedicated between your home and the DSL provider's central office
-- the providers offer little or no guarantee of bandwidth all the way
across the Internet.
DSL access is not as susceptible to packet sniffing as cable modem
access, but many of the other security risks we'll cover apply to both
DSL and cable modem access. (See the "Computer
security risks to home users" section of this document.)
- How are broadband services different from traditional dial-up
services?
Traditional dial-up Internet services are sometimes referred to as
"dial-on-demand" services. That is, your computer only connects to the
Internet when it has something to send, such as email or a request to
load a web page. Once there is no more data to be sent, or after a
8e6ain amount of idle time, the computer disconnects the call. Also,
in most cases each call connects to a pool of modems at the ISP, and
since the modem IP addresses are dynamically assigned, your computer
is usually assigned a different IP address on each call. As a result,
it is more difficult (not impossible, just difficult) for an attacker
to take advantage of vulnerable network services to take control of
your computer.
Broadband services are referred to as "always-on" services because
there is no call setup when your computer has something to send. The
computer is always on the network, ready to send or receive data
through its network interface card (NIC). Since the connection is
always up, your computer’s IP address will change less frequently (if
at all), thus making it more of a fixed target for attack.
What’s more, many broadband service providers use well-known IP
addresses for home users. So while an attacker may not be able to
single out your specific computer as belonging to you, they may at
least be able to know that your service providers’ broadband customers
are within a 8e6ain address range, thereby making your computer a
more likely target than it might have been otherwise.
The table below shows a brief comparison of traditional dial-up and
broadband services.
|
Dial-up |
Broadband |
| Connection type |
Dial on demand |
Always on |
| IP address |
Changes on each call |
Static or infrequently changing |
| Relative connection speed |
Low |
High |
| Remote control potential |
Computer must be dialed in to control remotely |
Computer is always connected, so remote control can occur
anytime |
| ISP-provided security |
Little or none |
Little or none |
|
Table 1: Comparison of Dial-up and
Broadband
Services |
- How is broadband access different from the network I use at
work?
Corporate and government networks are typically protected by many
layers of security, ranging from network firewalls to encryption. In
addition, they usually have support staff who maintain the security
and availability of these network connections.
Although your ISP is responsible for maintaining the services they
provide to you, you probably won’t have dedicated staff on hand to
manage and operate your home network. You are ultimately responsible
for your own computers. As a result, it is up to you to take
reasonable precautions to secure your computers from accidental or
intentional misuse.
- What is a protocol?
A protocol is a well-defined specification that allows computers to
communicate across a network. In a way, protocols define the "grammar"
that computers can use to "talk" to each other.
- What is IP?
IP stands for "Internet Protocol". It can be thought of as the
common language of computers on the Internet. There are a number of
detailed descriptions of IP given elsewhere, so we won't cover it in
detail in this document. However, it is important to know a few things
about IP in order to understand how to secure your computer. Here
we’ll cover IP addresses, static vs. dynamic addressing, NAT, and TCP
and UDP Ports.
An overview of TCP/IP can be found in the TCP/IP Frequently Asked
Questions (FAQ) at
- http://www.faqs.org/faqs/internet/tcp-ip/tcp-ip-faq/part1/
and
- http://www.faqs.org/faqs/internet/tcp-ip/tcp-ip-faq/part2/
- What is an IP address?
IP addresses are analogous to telephone numbers – when you want to
call someone on the telephone, you must first know their telephone
number. Similarly, when a computer on the Internet needs to send data
to another computer, it must first know its IP address. IP addresses
are typically shown as four numbers separated by decimal points, or
“dots”. For example, 10.24.254.3 and 192.168.62.231 are IP
addresses.
If you need to make a telephone call but you only know the person’s
name, you can look them up in the telephone directory (or call
directory services) to get their telephone number. On the Internet,
that directory is called the Domain Name System, or DNS for short. If
you know the name of a server, say www.8e6.org, and you type this
into your web browser, your computer will then go ask its DNS server
what the numeric IP address is that is associated with that name.
Every computer on the Internet has an IP address associated with it
that uniquely identifies it. However, that address may change over
time, especially if the computer is
- dialing into an Internet Service Provider (ISP)
- connected behind a network firewall
- connected to a broadband service using dynamic IP addressing.
- What are static and dynamic addressing?
Static IP addressing occurs when an ISP permanently assigns one or
more IP addresses for each user. These addresses do not change over
time. However, if a static address is assigned but not in use, it is
effectively wasted. Since ISPs have a limited number of addresses
allocated to them, they sometimes need to make more efficient use of
their addresses.
Dynamic IP addressing allows the ISP to efficiently utilize their
address space. Using dynamic IP addressing, the IP addresses of
individual user computers may change over time. If a dynamic address
is not in use, it can be automatically reassigned to another computer
as needed.
- What is NAT?
Network Address Translation (NAT) provides a way to hide the IP
addresses of a private network from the Internet while still allowing
computers on that network to access the Internet. NAT can be used in
many different ways, but one method frequently used by home users is
called "masquerading".
Using NAT masquerading, one or more devices on a LAN can be made to
appear as a single IP address to the outside Internet. This allows for
multiple computers in a home network to use a single cable modem or
DSL connection without requiring the ISP to provide more than one IP
address to the user. Using this method, the ISP-assigned IP address
can be either static or dynamic. Most network firewalls support NAT
masquerading.
- What are TCP and UDP Ports?
TCP (Transmission Control Protocol) and UDP (User Datagram
Protocol) are both protocols that use IP. Whereas IP allows two
computers to talk to each other across the Internet, TCP and UDP allow
individual applications (also known as "services") on those computers
to talk to each other.
In the same way that a telephone number or physical mail box might
be associated with more than one person, a computer might have
multiple applications (e.g. email, file services, web services)
running on the same IP address. Ports allow a computer to
differentiate services such as email data from web data. A port is
simply a number associated with each application that uniquely
identifies that service on that computer. Both TCP and UDP use ports
to identify services. Some common port numbers are 80 for web (HTTP),
25 for email (SMTP), and 53 for Dmain Name System (DNS).
- What is a firewall?
The Firewalls FAQ (http://www.faqs.org/faqs/firewalls-faq/)
defines a firewall as "a system or group of systems that enforces an
access control policy between two networks." In the context of home
networks, a firewall typically takes one of two forms:
- Software firewall - specialized software running on an
individual computer, or
- Network firewall - a dedicated device designed to protect
one or more computers.
Both types of firewall allow the user to define access policies for
inbound connections to the computers they are protecting. Many also
provide the ability to control what services (ports) the protected
computers are able to access on the Internet (outbound access). Most
firewalls intended for home use come with pre-configured security
policies from which the user chooses, and some allow the user to
customize these policies for their specific needs.
More information on firewalls can be found in the Additional
resources section of this document.
- What does antivirus software do?
There are a variety of antivirus software packages that operate in
many different ways, depending on how the vendor chose to implement
their software. What they have in common, though, is that they all
look for patterns in the files or memory of your computer that
indicate the possible presence of a known virus. Antivirus packages
know what to look for through the use of virus profiles (sometimes
called "signatures") provided by the vendor.
New viruses are discovered daily. The effectiveness of antivirus
software is dependent on having the latest virus profiles installed on
your computer so that it can look for recently discovered viruses. It
is important to keep these profiles up to date.
- Computer security risks to home users
- What is at risk?
Information security is concerned with three main areas:
- Confidentiality - information should be available only to those
who rightfully have access to it
- Integrity -- information should be modified only by those who
are authorized to do so
- Availability -- information should be accessible to those who
need it when they need it
These concepts apply to home Internet users just as much as they
would to any corporate or government network. You probably wouldn't
let a stranger look through your important documents. In the same way,
you may want to keep the tasks you perform on your computer
confidential, whether it's tracking your investments or sending email
messages to family and friends. Also, you should have some assurance
that the information you enter into your computer remains intact and
is available when you need it.
Some security risks arise from the possibility of intentional
misuse of your computer by intruders via the Internet. Others are
risks that you would face even if you weren't connected to the
Internet (e.g. hard disk failures, theft, power outages). The bad news
is that you probably cannot plan for every possible risk. The good
news is that you can take some simple steps to reduce the chance that
you'll be affected by the most common threats -- and some of those
steps help with both the intentional and accidental risks you're
likely to face.
Before we get to what you can do to protect your computer or home
network, let’s take a closer look at some of these risks.
- Intentional misuse of your computer
The most common methods used by intruders to gain control of home
computers are briefly described below. More detailed information is
available by reviewing the URLs listed in the References
section below.
- Trojan
horse programs
- Back
door and remote administration programs
- Denial
of service
- Being
an intermediary for another attack
- Unprotected
Windows shares
- Mobile
code (Java, JavaScript, and ActiveX)
- Cross-site
scripting
- Email
spoofing
- Email-borne
viruses
- Hidden
file extensions
- Chat
clients
- Packet
sniffing
- Trojan horse programs
Trojan horse programs are a common way for intruders to trick you
(sometimes referred to as "social engineering") into installing
"back door" programs. These can allow intruders easy access to your
computer without your knowledge, change your system configurations,
or infect your computer with a computer virus. More information
about Trojan horses can be found in the following document.
- http://www.8e6.org/advisories/CA-1999-02.html
- Back door and remote administration programs
On Windows computers, three tools commonly used by intruders to
gain remote access to your computer are BackOrifice, Netbus, and
SubSeven. These back door or remote administration programs, once
installed, allow other people to access and control your computer.
- Denial of service
Another form of attack is called a denial-of-service (DoS)
attack. This type of attack causes your computer to crash or to
become so busy processing data that you are unable to use it. In
most cases, the latest patches will prevent the attack. The
following documents describe denial-of-service attacks in greater
detail.
It is important to note that in addition to being the target of a
DoS attack, it is possible for your computer to be used as a
participant in a denial-of-service attack on another system.
- Being an intermediary for another attack
Intruders will frequently use compromised computers as launching
pads for attacking other systems. An example of this is how
distributed denial-of-service (DDoS) tools are used. The intruders
install an "agent" (frequently through a Trojan horse program) that
runs on the compromised computer awaiting further instructions.
Then, when a number of agents are running on different computers, a
single "handler" can instruct all of them to launch a
denial-of-service attack on another system. Thus, the end target of
the attack is not your own computer, but someone else’s -- your
computer is just a convenient tool in a larger attack.
- Unprotected Windows shares
Unprotected Windows networking shares can be exploited by
intruders in an automated way to place tools on large numbers of
Windows-based computers attached to the Internet. Because site
security on the Internet is interdependent, a compromised computer
not only creates problems for the computer's owner, but it is also a
threat to other sites on the Internet. The greater immediate risk to
the Internet community is the potentially large number of computers
attached to the Internet with unprotected Windows networking shares
combined with distributed attack tools such as those described
in
-
Another threat includes malicious and destructive code, such as
viruses or worms, which leverage unprotected Windows networking
shares to propagate. One such example is the 911 worm described
in
-
There is great potential for the emergence of other intruder
tools that leverage unprotected Windows networking shares on a
widespread basis.
- Mobile code (Java/JavaScript/ActiveX)
There have been reports of problems with "mobile code" (e.g.
Java, JavaScript, and ActiveX). These are programming languages that
let web developers write code that is executed by your web browser.
Although the code is generally useful, it can be used by intruders
to gather information (such as which web sites you visit) or to run
malicious code on your computer. It is possible to disable Java,
JavaScript, and ActiveX in your web browser. We recommend that you
do so if you are browsing web sites that you are not familiar with
or do not trust.
Also be aware of the risks involved in the use of mobile code
within email programs. Many email programs use the same code as web
browsers to display HTML. Thus, vulnerabilities that affect Java,
JavaScript, and ActiveX are often applicable to email as well as web
pages.
More information on ActiveX security is available in
- Cross-site scripting
A malicious web developer may attach a script to something sent
to a web site, such as a URL, an element in a form, or a database
inquiry. Later, when the web site responds to you, the malicious
script is transferred to your browser.
You can potentially expose your web browser to malicious scripts
by
- following links in web pages, email messages, or newsgroup
postings without knowing what they link to
- using interactive forms on an untrustworthy site
- viewing online discussion groups, forums, or other dynamically
generated pages where users can post text containing HTML tags
More information regarding the risks posed by malicious code in
web links can be found in .
- Email spoofing
Email “spoofing” is when an email message appears to have
originated from one source when it actually was sent from another
source. Email spoofing is often an attempt to trick the user into
making a damaging statement or releasing sensitive information (such
as passwords).
Spoofed email can range from harmless pranks to social
engineering ploys. Examples of the latter include
- email claiming to be from a system administrator requesting
users to change their passwords to a specified string and
threatening to suspend their account if they do not comply
- email claiming to be from a person in authority requesting
users to send them a copy of a password file or other sensitive
information
Note that while service providers may occasionally request that
you change your password, they usually will not specify what
you should change it to. Also, most legitimate service providers
would never ask you to send them any password information via
email. If you suspect that you may have received a spoofed email
from someone with malicious intent, you should contact your service
provider's support personnel immediately.
- Email borne viruses
Viruses and other types of malicious code are often spread as
attachments to email messages. Before opening any attachments, be
sure you know the source of the attachment. It is not enough that
the mail originated from an address you recognize. The Melissa virus
(see References)
spread precisely because it originated from a familiar address.
Also, malicious code might be distributed in amusing or enticing
programs.
Never run a program unless you know it to be authored by a person
or company that you trust. Also, don't send programs of unknown
origin to your friends or coworkers simply because they are amusing
-- they might contain a Trojan horse program.
- Hidden file extensions
Windows operating systems contain an option to "Hide file
extensions for known file types". The option is enabled by default,
but a user may choose to disable this option in order to have file
extensions displayed by Windows. Multiple email-borne viruses are
known to exploit hidden file extensions. The first major attack that
took advantage of a hidden file extension was the VBS/LoveLetter
worm which contained an email attachment named
"LOVE-LETTER-FOR-YOU.TXT.vbs". Other malicious programs have since
incorporated similar naming schemes. Examples include
- Downloader (MySis.avi.exe or QuickFlick.mpg.exe)
- VBS/Timofonica (TIMOFONICA.TXT.vbs)
- VBS/CoolNote (COOL_NOTEPAD_DEMO.TXT.vbs)
- VBS/OnTheFly (AnnaKournikova.jpg.vbs)
The files attached to the email messages sent by these viruses
may appear to be harmless text (.txt), MPEG (.mpg), AVI (.avi) or
other file types when in fact the file is a malicious script or
executable (.vbs or .exe, for example).
- Chat clients
Internet chat applications, such as instant messaging
applications and Internet Relay Chat (IRC) networks, provide a
mechanism for information to be transmitted bi-directionally between
computers on the Internet. Chat clients provide groups of
individuals with the means to exchange dialog, web URLs, and in many
cases, files of any type.
Because many chat clients allow for the exchange of executable
code, they present risks similar to those of email clients. As with
email clients, care should be taken to limit the chat client’s
ability to execute downloaded files. As always, you should be wary
of exchanging files with unknown parties.
- Packet sniffing
A packet sniffer is a program that captures data from information
packets as they travel over the network. That data may include user
names, passwords, and proprietary information that travels over the
network in clear text. With perhaps hundreds or thousands of
passwords captured by the packet sniffer, intruders can launch
widespread attacks on systems. Installing a packet sniffer does not
necessarily require administrator-level access.
Relative to DSL and traditional dial-up users, cable modem users
have a higher risk of exposure to packet sniffers since entire
neighborhoods of cable modem users are effectively part of the same
LAN. A packet sniffer installed on any cable modem user's computer
in a neighborhood may be able to capture data transmitted by any
other cable modem in the same neighborhood.
- Accidents and other risks
In addition to the risks associated with connecting your computer
to the Internet, there are a number of risks that apply even if the
computer has no network connections at all. Most of these risks are
well-known, so we won’t go into much detail in this document, but it
is important to note that the common practices associated with
reducing these risks may also help reduce susceptibility to the
network-based risks discussed above.
- Disk failure
Recall that availability is one of the three key elements of
information security. Although all stored data can become
unavailable -- if the media it’s stored on is physically damaged,
destroyed, or lost -- data stored on hard disks is at higher risk
due to the mechanical nature of the device. Hard disk crashes are a
common cause of data loss on personal computers. Regular system
backups are the only effective remedy.
- Power failure and surges
Power problems (surges, blackouts, and brown-outs) can cause
physical damage to a computer, inducing a hard disk crash or
otherwise harming the electronic components of the computer. Common
mitigation methods include using surge suppressors and
uninterruptible power supplies (UPS).
- Physical Theft
Physical theft of a computer, of course, results in the loss of
confidentiality and availability, and (assuming the computer is ever
recovered) makes the integrity of the data stored on the disk
suspect. Regular system backups (with the backups stored somewhere
away from the computer) allow for recovery of the data, but backups
alone cannot address confidentiality. Cryptographic tools are
available that can encrypt data stored on a computer’s hard disk.
The 8e6/CC encourages the use of these tools if the computer
contains sensitive data or is at high risk of theft (e.g. laptops or
other portable computers).
- Actions home users can take to protect their computer systems
The 8e6/CC recommends the following practices to home users:
- Consult
your system support personnel if you work from home
- Use
virus protection software
- Use a
firewall
- Don’t
open unknown email attachments
- Don’t
run programs of unknown origin
- Disable
hidden filename extensions
- Keep
all applications (including your operating system) patched
- Turn
off your computer or disconnect from the network when not in use
- Disable
Java, JavaScript, and ActiveX if possible
- Disable
scripting features in email programs
- Make
regular backups of critical data
- Make a
boot disk in case your computer is damaged or compromised
Further discussion on each of these points is given below.
Recommendations
- Consult your system support personnel if you work from home
If you use your broadband access to connect to your employer's
network via a Virtual Private Network (VPN) or other means, your
employer may have policies or procedures relating to the security of
your home network. Be sure to consult with your employer's support
personnel, as appropriate, before following any of the steps outlined
in this document.
- Use virus protection software
The 8e6/CC recommends the use of anti-virus software on all
Internet-connected computers. Be sure to keep your anti-virus software
up-to-date. Many anti-virus packages support automatic updates of
virus definitions. We recommend the use of these automatic updates
when available.
- Use a firewall
We strongly recommend the use of some type of firewall product,
such as a network appliance or a personal firewall software package.
Intruders are constantly scanning home user systems for known
vulnerabilities. Network firewalls (whether software or
hardware-based) can provide some degree of protection against these
attacks. However, no firewall can detect or stop all attacks, so it’s
not sufficient to install a firewall and then ignore all other
security measures.
- Don't open unknown email attachments
Before opening any email attachments, be sure you know the source
of the attachment. It is not enough that the mail originated from an
address you recognize. The Melissa virus spread precisely because it
originated from a familiar address. Malicious code might be
distributed in amusing or enticing programs.
If you must open an attachment before you can verify the source, we
suggest the following procedure:
- be sure your virus definitions are up-to-date (see "Use
virus protection software" above)
- save the file to your hard disk
- scan the file using your antivirus software
- open the file
For additional protection, you can disconnect your computer's
network connection before opening the file.
Following these steps will reduce, but not wholly eliminate, the
chance that any malicious code contained in the attachment might
spread from your computer to others.
- Don't run programs of unknown origin
Never run a program unless you know it to be authored by a person
or company that you trust. Also, don't send programs of unknown origin
to your friends or coworkers simply because they are amusing -- they
might contain a Trojan horse program.
- Disable hidden filename extensions
Windows operating systems contain an option to "Hide file
extensions for known file types". The option is enabled by default,
but you can disable this option in order to have file extensions
displayed by Windows. After disabling this option, there are still
some file extensions that, by default, will continue to remain
hidden.
There is a registry value which, if set, will cause Windows to hide
8e6ain file extensions regardless of user configuration choices
elsewhere in the operating system. The "NeverShowExt" registry value
is used to hide the extensions for basic Windows file types. For
example, the ".LNK" extension associated with Windows shortcuts
remains hidden even after a user has turned off the option to hide
extensions.
Specific instructions for disabling hidden file name extensions are
given in
- Keep all applications, including your operating system,
patched
Vendors will usually release patches for their software when a
vulnerability has been discovered. Most product documentation offers a
method to get updates and patches. You should be able to obtain
updates from the vendor's web site. Read the manuals or browse the
vendor's web site for more information.
Some applications will automatically check for available updates,
and many vendors offer automatic notification of updates via a mailing
list. Look on your vendor's web site for information about automatic
notification. If no mailing list or other automated notification
mechanism is offered you may need to check periodically for
updates.
- Turn off your computer or disconnect from the network when not in
use
Turn off your computer or disconnect its Ethernet interface when
you are not using it. An intruder cannot attack your computer if it is
powered off or otherwise completely disconnected from the network.
- Disable Java, JavaScript, and ActiveX if possible
Be aware of the risks involved in the use of "mobile code" such as
ActiveX, Java, and JavaScript. A malicious web developer may attach a
script to something sent to a web site, such as a URL, an element in a
form, or a database inquiry. Later, when the web site responds to you,
the malicious script is transferred to your browser.
The most significant impact of this vulnerability can be avoided by
disabling all scripting languages. Turning off these options will keep
you from being vulnerable to malicious scripts. However, it will limit
the interaction you can have with some web sites.
Many legitimate sites use scripts running within the browser to add
useful features. Disabling scripting may degrade the functionality of
these sites.
More information on ActiveX security, including recommendations for
users who administer their own computers, is available in
More information regarding the risks posed by malicious code in web
links can be found in .
- Disable scripting features in email programs
Because many email programs use the same code as web browsers to
display HTML, vulnerabilities that affect ActiveX, Java, and
JavaScript are often applicable to email as well as web pages.
Therefore, in addition to disabling scripting features in web browsers
(see "Disable
Java, JavaScript, and ActiveX if possible", above), we recommend
that users also disable these features in their email programs.
- Make regular backups of critical data
Keep a copy of important files on removable media such as ZIP disks
or recordable CD-ROM disks (CD-R or CD-RW disks). Use software backup
tools if available, and store the backup disks somewhere away from the
computer.
- Make a boot disk in case your computer is damaged or
compromised
To aid in recovering from a security breach or hard disk failure,
create a boot disk on a floppy disk which will help when recovering a
computer after such an event has occurred. Remember, however, you must
create this disk before you have a security
event.
Appendix
References and additional information
This section contains links to references
and additional
resources related to this document.
References
- The following documents were used in compiling portions of this
document:
8e6 Advisories
- CA-1999-02: Trojan Horses
-
- CA-1999-04: Melissa Macro Virus
-
- CA-2000-01: Denial-of-Service Developments
-
- CA-2000-02: Malicious HTML Tags Embedded in Client Web Requests
-
- CA-2001-22: W32/Sircam Malicious Code
8e6 Incident Notes
- IN-2000-01: Windows Based DDOS Agents
-
- IN-2000-02: Exploitation of Unprotected Windows Networking Shares
-
- IN-2000-03: 911 Worm
-
- IN-2000-07: Exploitation of Hidden File Extensions
-
- IN-2000-08: Chat Clients and Network Security
-
- IN-2001-15: W32/Goner Worm
8e6 Tech Tips
- Spoofed/Forged Email
-
Other 8e6 documents
- Results of the Security in ActiveX Workshop
-
- Security of the Internet
-
- Trends in Denial of Service Attack Technology
Additional resourcesAdditional
information is available from the following sources.
- TCP/IP Frequently Asked Questions
- Computer Virus Frequently Asked Questions for New Users
-
- alt.comp.virus Frequently Asked Questions
- VIRUS-L/comp.virus Frequently Asked Questions
-
- Firewalls Frequently Asked Questions
This document is available from:
8e6/CC Contact Information
Email: security@8e6.com.cn Phone: +86
532-8758-2008 (24-hour hotline) Fax: +86 532-8758-8888 Postal address:
- 1097 Shangri-La room, Qingdao, Shandong, China
Using encryption
We strongly urge you to encrypt sensitive information sent by email.
Our public PGP key is available from
If you prefer to use DES, please call the 8e6 hotline for more
information.
Getting security information
8e6 publications and other security information are available from
our web site
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