 PC Advice
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Viruses |
Computer viruses have existed for many years; the first instances I'm aware of date to the 1970s. Sometimes they begin as jokes, but frequently get out of hand and wreak havoc in a much wider context than was ever intended. In other cases, they're created with malicious intent and can either destroy or corrupt data on infected machines. A more recent development, fueled by the increased availability of always-on DSL and Cable networking in the home, involves data theft or the hijacking of machines for use in a botnet or other illegal activity.
The best viruses are insidious, and capable of escaping detection until it's too late. They may arrive at your computer through a variety of vectors, including:
- Inclusion in an E-mail Message. In this case, an executable file (.exe) is sent to someone's account. The virus payload is installed when the attachment is activated by the recipient, who is somehow enticed into double-clicking on the icon. Such attachments may arrive in the guise of "a new patch from Microsoft," a "screen pet," a slide show, or a free utility. Spam mail often is used in virus transmission attempts.
- Inclusion in another executable. This is sometimes known as "piggybacking," since a virus attaches itself invisibly to a valid application as a method of transporting itself from one machine to another. The virus is transmitted as soon as the application is activated.
- A Web URL. In this case, you receive a message containing a clickable link to a Web site, perhaps offering a free service or some other enticement. When you activate the link, the Web site attempts to install a virus via a browser flaw or other open doorway into your system. It's also possible for virus code to be included in the HTML message itself, which means you may not even need to click on the link.
- Direct Network Access. Any computer connected to any network is potentially vulnerable to attack, no matter which OS is in use. TCP/IP networks use individually numbered "sockets" or "ports" when connecting to other machines. Some, like SMTP mail, telnet, or FTP, use "well known" port numbers that have been targeted for attack in the past. Some viruses scan for open ports on networked machines, then attempt to break into these systems using known or newly developed methods. Once inside, they can install copies of themselves or other illicit applications, such as spyware and botnet software.
Viruses often disguise themselves; I've seen cases where a virus has replaced a legitimate Windows utility or system file and continues to provide the functionality of the original while attempting to propagate itself to other machines.
How Do I Avoid Infection?
First and foremost, you should install and maintain a good antivirus program (Norton, MacAfee, Zone Alarm, et.al.) on every machine you own. Maintenance is important, since virus signatures constantly change as variants and new types appear; many antivirus applications today perform daily signature updates.
The rest of the equation involves, as usual, vigilance and deliberate action.
- Don't automatically click on attachments or URLs in E-mail messages, especially if they were sent by people you don't know.
- Don't install unknown software. While many Web sites offering free Windows applications now thoroughly check all new shareware and freeware applications for viruses, this is not always the case. Know where an application came from, and make sure the vendor is legitimate.
- If your machine is networked, even just via modem, make sure it's fully patched and running a good firewall application that's also fully patched.
- Don't do all your work while logged into an account with Windows administrative privileges. Set up and use a less privileged account unless you need to install new software or change system settings.
- Last, don't install network applications you don't need. Just because your Windows Server or XP box can act as a Telnet, FTP, or Web server doesn't mean you should run those applications, since they often require special security steps in order to prevent intrusion.
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