Sunday, February 8, 2009

Prevent Virus Infections #2

Rule #1: Download only from reputable sources

Adhering to this single rule will cut your risk of infection dramatically. So, what is a "reputable source"? Certainly the following:

1. Any major download site like, or
2. Any site of a reputable developer or vendor, such as Microsoft, Google, HP or Dell.
3. Any open-source software hosted on, and other large open- source hangouts.

Of course there are many more "reputable sources." The secret is in knowing which sites to trust. McAfee SiteAdvisor is a free plug-in for Internet Explorer and Firefox (download page) that rates sites based on a number of security criteria, including whether the downloads from the site are free from malware. If a site has SiteAdvisor's "green" rating, you can be pretty sure it's safe. Conversely, you can count on any site with a "Red" rating as being unsafe.

So, what files are definitely unsafe to download or install?

Topping the list are files a site offers to you all by itself or via a popup window. If the site asks whether you'd like to install a toolbar, video viewer, download manager, or whatever, always say no. Such files are the riskiest of all downloads, so never be tempted. Make no exception here; this is seriously dangerous territory.

Other unsafe sources are file-sharing services. Never download software from BitTorrent and other file-sharing networks unless you can verify the authenticity and integrity of the download with 100% certainty. For most people, it's best to play it safe and never download from these services.

The same prohibition applies to software provided to you by friends, classmates or colleagues. Unless it's on the original manufacturer's CD, there's no way you can verify the authenticity and integrity of the program.

Rule #2: Scan all downloaded files

Normally, you don't have to worry about scanning files you download, because most of the top antivirus programs automatically scan a file when you download it. If you're unsure whether your security product scans downloaded files automatically, you can usually initiate a manual scan by right-clicking the downloaded file and selecting the "Scan this file" option before you run it.

Unfortunately, even the best virus scanners have a less-than-100% detection rate; a downloaded file may scan as clean yet still be infected.

You can further reduce the chance of a file being infected by making use of a free Web-based scanning service, such as Jotti and Virus Total. These sites run your downloaded file through a dozen or more antivirus and anti-malware programs.

Of course, there's still a chance your download is infected, even if it passes all the tests at Jotti or Virus Total. However, the protection these services offer is good enough to keep most PCs safe.

Continued in Prevent Virus Infections #3

As usual I welcome comments and suggestions right here in the blog.

Thank you in advance.

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