Add General Atlantic (GA) to the list of buyout firms that has picked up a stake in an information security vendor. The firm on Thursday acquired a 20% chunk of Russian antivirus software provider Kaspersky Lab for $200m, implying an overall valuation of $1bn. The deal marks the third significant investment by a private equity (PE) shop in a European anti-malware vendor in just the past six months.

GA also appears to have gotten a bargain in becoming the company’s second-largest shareholder. Kasperky’s $1bn valuation works out to about 2 times sales and 8-9x EBITDA, according to our understanding. For comparison, rival anti-malware vendor Sophos got more than 3x trailing sales when it sold a majority stake to Apax Partners last May. (And according to at least two sources, Kaspersky was targeting a valuation of ‘well north’ of $1bn when it was running the process, which took most of 2010.) The third recent antivirus deal was Summit Partners’ $100m investment in AVAST Software last August.