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.
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 (Denial-of-Service Attacks )
How can you protect yourself?
* Use and maintain anti-virus software – 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. 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. If your email program automatically downloads attachments, check your settings to see if you can disable this feature.
* 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. 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 . 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 . Apply the highest level of security available that still gives you the functionality you need.