First detected back in March, the 'Gumblar' attacks have been gaining steam lately, growing by as much as 188 percent in just a single week, ScanSafe warned. Gumblar refers to a Web attack that plants malicious scripts on normally legitimate websites, which then redirects Google search results on victims' PCs.

"A typical series of website compromises reaches peak within the first week or so and subsequently begins declining in intensity as detection is added by signature vendors, user awareness increases and website operators begin cleaning the affected sites," ScanSafe senior security researcher Mary Landesman, said late last week in an advisory.

In Gumblar's case, the opposite has been true, a result of website administrators being affected by the attacks. According to ScanSite, some well known sites have fallen prey to Gumblar include Tennis.com, Variety.com, and Coldwellbanker.com.

Keep those virus definitions up to date, and if you haven't done so already, look into installing an AV app.

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