Cyber Security Tip ST06-008

                            Safeguarding Your Data

 

   When there are multiple people using your computer and/or you store

   sensitive personal and work-related data on your computer, it is especially

   important to take extra security precautions.

 

Why isn't "more" better?

 

   Maybe there is an extra software program included with a program you bought.

   Or perhaps you found a free download online. You may be tempted to install

   the programs just because you can, or because you think you might use them

   later. However, even if the source and the software are legitimate, there

   may  be hidden risks. And if other people use your computer, there are

   additional risks.

 

   These risks become especially important if you use your computer to manage

   your personal finances (banking, taxes, online bill payment, etc.), store

   sensitive personal data, or perform work-related activities away from the

   office. However, there are steps you can take to protect yourself.

 

How can you protect both your personal and work-related data?

 

     * Use and maintain anti-virus software and a firewall - Protect yourself

       against viruses and Trojan horses that may steal or modify the data on

       your own computer and leave you vulnerable by using anti-virus software

       and a firewall (see Understanding Anti-Virus Software and Understanding

       Firewalls  for  more  information).  Make  sure to keep your virus

       definitions up to date.

     * Regularly scan your computer for spyware - Spyware or adware hidden in

       software programs may affect the performance of your computer and give

       attackers access to your data. Use a legitimate anti-spyware program to

       scan your computer and remove any of these files (see Recognizing and

       Avoiding Spyware for more information). Many anti-virus products have

       incorporated spyware detection.

     * Keep software up to date - Install software patches so that attackers

       cannot  take  advantage  of known problems or vulnerabilities (see

       Understanding Patches for more information). Many operating systems

       offer automatic updates. If this option is available, you should turn it

       on.

     * Evaluate  your  software's settings - The default settings of most

       software enable all available functionality. However, attackers may be

       able to take advantage of this functionality to access your computer. It

       is especially important to check the settings for software that connects

       to the internet (browsers, email clients, etc.). Apply the highest level

       of security available that still gives you the functionality you need.

     * Avoid unused software programs - Do not clutter your computer with

       unnecessary software programs. If you have programs on your computer

       that  you  do  not use, consider uninstalling them. In addition to

       consuming system resources, these programs may contain vulnerabilities

       that, if not patched, may allow an attacker to access your computer.

     * Consider creating separate user accounts - If there are other people

       using  your  computer,  you  may  be worried that someone else may

       accidentally access, modify, and/or delete your files. Most operating

       systems (including Windows XP and Vista, Mac OS X, and Linux) give you

       the option of creating a different user account for each user, and you

       can set the amount of access and privileges for each account. You may

       also  choose  to have separate accounts for your work and personal

       purposes. While this approach will not completely isolate each area, it

       does offer some additional protection. However, it will not protect your

       computer against vulnerabilities that give an attacker administrative

       privileges. Ideally, you will have separate computers for work and

       personal use; this will offer a different type of protection.

     * Establish guidelines for computer use - If there are multiple people

       using your computer, especially children, make sure they understand how

       to  use  the  computer and internet safely. Setting boundaries and

       guidelines will help to protect your data (see Keeping Children Safe

       Online for more information).

     * Use passwords and encrypt sensitive files - Passwords and other security

       features add layers of protection if used appropriately (see Choosing

       and  Protecting  Passwords  and  Supplementing  Passwords for more

       information). By encrypting files, you ensure that unauthorized people

       can't view data even if they can physically access it. You may also want

       to consider options for full disk encryption, which prevents a thief

       from  even starting your laptop without a passphrase. When you use

       encryption, it is important to remember your passwords and passphrases;

       if you forget or lose them, you may lose your data.

     * Follow  corporate  policies  for handling and storing work-related

       information - If you use your computer for work-related purposes, make

       sure to follow any corporate policies for handling and storing the

       information.  These  policies  were  likely established to protect

       proprietary information and customer data, as well as to protect you and

       the company from liability. Even if it is not explicitly stated in your

       corporate policy, you should avoid allowing other people, including

       family members, to use a computer that contains corporate data.

     * Dispose of sensitive information properly - Simply deleting a file does

       not completely erase it. To ensure that an attacker cannot access these

       files,  make  sure  that you adequately erase sensitive files (see

       Effectively Erasing Files for more information).

     * Follow good security habits - Review other security tips for ways to

       protect yourself and your data.

     _________________________________________________________________

 

     Author: Mindi McDowell

     _________________________________________________________________

 

     Produced 2006 by US-CERT, a government organization.

 

     Note: This tip was previously published and is being re-distributed

     to increase awareness.

  

     Terms of use

 

     <http://www.us-cert.gov/legal.html>

 

     This document can also be found at

 

     <http://www.us-cert.gov/cas/tips/ST06-008.html>

Updated  Wednesday, February 18, 2009

 

Benjamin

Computer

Services, Inc.

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National Cyber Alert System
Cyber Security Tip ST06-006 archive
 

Understanding Hidden Threats: Corrupted Software Files

Malicious code is not always hidden in web page scripts or unusual file formats. Attackers may corrupt types of files that you would recognize and typically consider safe, so you should take precautions when opening files from other people.

 

What types of files can attackers corrupt?

An attacker may be able to insert malicious code into any file, including common file types that you would normally consider safe. These files may include documents created with word processing software, spreadsheets, or image files. After corrupting the file, an attacker may distribute it through email or post it to a web site. Depending on the type of malicious code, you may infect your computer by just opening the file.

When corrupting files, attackers often take advantage of vulnerabilities that they discover in the software that is used to create or open the file. These vulnerabilities may allow attackers to insert and execute malicious scripts or code, and they are not always detected. Sometimes the vulnerability involves a combination of certain files (such as a particular piece of software running on a particular operating system) or only affects certain versions of a software program.

What problems can malicious files cause?

There are various types of malicious code, including viruses, worms, and Trojan horses (see Why is Cyber Security a Problem? for more information). However, the range of consequences varies even within these categories. The malicious code may be designed to perform one or more functions, including

  • interfering with your computer's ability to process information by consuming memory or bandwidth (causing your computer to become significantly slower or even "freeze")
  • installing, altering, or deleting files on your computer
  • giving the attacker access to your computer
  • using your computer to attack other computers (see Understanding Denial-of-Service Attacks for more information)

How can you protect yourself?

  • Use and maintain anti-virus software - Anti-virus software recognizes and protects your computer against most known viruses, so you may be able to detect and remove the virus before it can do any damage (see Understanding Anti-Virus Software for more information). Because attackers are continually writing new viruses, it is important to keep your definitions up to date.

     

  • Use caution with email attachments - Do not open email attachments that you were not expecting, especially if they are from people you do not know. If you decide to open an email attachment, scan it for viruses first (see Using Caution with Email Attachments for more information). Not only is it possible for attackers to "spoof" the source of an email message, but your legitimate contacts may unknowingly send you an infected file.

     

  • Be wary of downloadable files on web sites - Avoid downloading files from sites that you do not trust. If you are getting the files from a supposedly secure site, look for a web site certificate (see Understanding Web Site Certificates for more information). If you do download a file from a web site, consider saving it to your computer and manually scanning it for viruses before opening it.

     

  • Keep software up to date - Install software patches so that attackers cannot take advantage of known problems or vulnerabilities (see Understanding Patches for more information). Many operating systems offer automatic updates. If this option is available, you should enable it.

     

  • Take advantage of security settings - Check the security settings of your email client and your web browser (see Evaluating Your Web Browser's Security Settings for more information). Apply the highest level of security available that still gives you the functionality you need.

Related information

Author: Mindi McDowell
Produced 2006 by US-CERT, a government organization. Terms of use
US-CERT
Last updated January 7, 2009

 

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