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Symantec revises opinion on attack code

Antivirus company Symantec backtracked on Wednesday after claiming that it captured an example of a new internet worm that takes advantage of a hole in Windows machines running Secure Sockets Layer (SSL).

On Tuesday, the company trapped an example of the malicious code, called backdoor.mipsiv., and warned customers that it was either a new worm or small automated program called a "bot" that exploits a Windows Private Communications Transport Protocol (PCT) vulnerability, part of the Windows implementation of SSL.

However, Symantec said yesterday that further analysis of the code showed that it was neither a worm nor a bot, and did not use the PCT vulnerability.

Instead, the code, still called backdoor.mipsiv, is described as a Trojan program. Mipsiv is placed on vulnerable machines by malicious hackers, after which it opens communications ports on systems it compromises and uses Internet Relay chat (IRC) channels to send instructions, Symantec said.
 
"We better understand what it's doing now and after further investigation, it doesn't look like it's self propagating," said Jonah Paransky, senior manager of security product management at Symantec.

Symantec's confusion stemmed from its misinterpretation of a series of related, but isolated events, he added.

Malicious hackers have been scanning for machines that have the PCT vulnerability, then using exploit code targeting that security hole to compromise those systems and place the mipsiv Trojan on them. Once installed, mipsiv communicates with the rest of the Internet through the same communications port, 443, that is used by PCT.

However, the Mipsiv code does not contain either worm or bot features and could only have been placed on systems by attackers who compromised the system using the PCT exploit code, or other means.

That means that the effects of the PCT exploit will be felt on targeted networks, whereas a worm or virus that used it could harm systems across the internet, Symantec said.

Microsoft warned customers about the buffer overrun vulnerability in PCT on 13 April and issued a software patch for affected systems. According to the company's security advisory, MS04-011, the PCT hole could allow a remote attacker to take complete control of affected systems. (See: http://www.microsoft.com/technet/security/bulletin/ms04-011.mspx.)

Sample computer code to exploit the hole appeared on the internet within days of Microsoft's warning, prompting the company to issue a warning to customers about the malicious activity. (See: http://www.microsoft.com/security/incident/pctdisable.asp.)

Other security experts that monitor malicious activity on the internet had been warning of increased attacks that use the SSL vulnerability and postulated that a worm may be responsible, but nobody has captured a copy of the malicious code.

The Sans Institute's Internet Storm Center said on Tuesday that it received reports of exploits using the SSL PCT hole and systematic scanning of networks for vulnerable systems, which indicated some kind of "automated tool".

Antivirus and security technology companies compete intensely to be the first to spot and even name new Internet threats like worms and viruses.

Symantec did not jump the gun in an attempt to be the first company to spot the new threat, Paransky said. "This is a classic tension in the community between letting customers know early and letting them know more information."

The danger posed by the PCT vulnerability and its widespread impact prompted the quick response from the company, which also raised its ThreatCon Rating of global network activity to level three or "high" alert, indicating that an "isolated threat to the computing infrastructure is currently under way or ... malicious code reaches a severe risk rating", according to the company's web page.

Symantec will leave the ThreatCon Rating in place for at least 24 hours, although Paransky could not comment on whether it would be lowered after that. 

Despite the false alarm with mipsiv, the increase in scanning for machines vulnerable to the PCT exploit means that a true worm or other automated attack is likely in the future, he said.

Paul Roberts writes for IDG News Service


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