Researchers have found evidence suggesting that the United States may have developed three computer viruses for use in espionage operations or cyber warfare.

A Reuters report said that Symantec Corp of the United States and Kaspersky Lab of Russia disclosed that they have found evidence that Flame's operators may have also worked with three other viruses that have yet to be discovered.

Current and former U.S. government sources also told Reuters that the United States was behind Stuxnet. Kaspersky and Symantec linked Stuxnet to Flame in June, saying that part of the Flame program is nearly identical to code found in a 2009 version of Stuxnet.

For now, the two firms know very little about the newly identified viruses, except that one of them is currently deployed in the Middle East. They are not sure what the malicious software was designed to do, the report said.  

Kaspersky and Symantec released their findings in reports describing analysis of "command and control" servers used to communicate with and control computers infected with Flame, said the report.

Researchers from both firms said the Flame operation was managed using a piece of software named "Newsforyou" that was built by a team of four software developers starting in 2006, the Reuters report said.

It was designed to look like a common program for managing content on websites, which was likely done in a bid to disguise its real purpose from hosting providers or investigators so that the operation would not be compromised, Kaspersky said in its report. 

Kaspersky Lab said it believes that SP, SPE and IP were espionage or sabotage tools separate from Flame. Symantec said it was not sure if they were simply variations of Flame or completely different pieces of software, said the report.