Later versions of the malware exploited weaknesses in the Java programming language to allow the code to be installed from bogus sites without the user's permission.
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Dr Web said that once the Trojan was installed it sent a message to the intruder's control server with a unique ID to identify the infected machine.
"By introducing the code criminals are potentially able to control the machine," the firm's chief executive Boris Sharov told the BBC.
"We stress the word potential as we have never seen any malicious activity since we hijacked the botnet to take it out of criminals' hands. However, we know people create viruses to get money.
"The largest amounts of bots - based on the IP addresses we identified - are in the US, Canada, UK and Australia, so it appears to have targeted English-speaking people."
Hits Apple at its corp
Dr Web also notes that 274 of the infected computers it detected appeared to be located in Cupertino, California - home to Apple's headquarters.