Attackers are exploiting a RealPlayer zero-day flaw to gain control of Windows systems through Internet Explorer, Symantec warned customers of its DeepSight Threat Analyst service late Oct. 18.
The unpatched vulnerability affects all versions of RealPlayer, including the most recent, 10.5, as well as the beta of RealPlayer 11, Symantec told eWEEK.
The zero-day vulnerability involves an ActiveX object in the RealPlayer component ierpplug.dll. Its not the first time this DLL has been exploited, but its the worst, given that only remote denial of service has been previously achieved.
"It appears that the miscreants have refined their technique to achieve code execution," Javier Santoyo, a manager at Symantec Security Response, said in a blog posting on Oct. 19.
The malware is being served on malicious Web sites. Santoyo told eWEEK in an interview that Symantec is unsure of how many sites are serving it up but that its a targeted attack against a Symantec customer. "Were not sure how the social engineering is being done" to get the customers employees to visit the rigged sites, he said. "I expect specific employees or groups are being sent e-mails. So the bad guys know which sites are being used more frequently by those [customers employees] and are targeting those sites."
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Santoyo was unable to say how many systems have been affected at the targeted company, but anybody who has RealPlayer installed could be at risk of exploit simply by visiting a malicious site; the player does not have to be running for the exploit to be successful.
After a victim has been lured to a rigged site, the malware is checking the targeted PC to determine if the installed version of RealPlayer is vulnerable. The sample of code Symantec received, Trojan.Reapall, exploits the RealPlayer vulnerability and then downloads and executes a copy of a Trojan called Trojan.Zonebac. If so, an attacker can potentially take over the targeted system.
Symantec said that if the vulnerability is successfully exploited, the malware triggers the playing of a clip called "videotest" from the "My Library" folder, available in standard installations of RealPlayer.
Until patches are available, Symantec offered these mitigating strategies:
- Set the kill bit on the Class identifier (CLSID) FDC7A535-4070-4B92-A0EA-D9994BCC0DC5, (see instructions here.
- Ensure that all Microsoft Internet Explorer clients are configured to prompt before executing Active Scripting. If Active Scripting is not required it should be disabled completely.
- Configure all Microsoft Outlook and Outlook Express clients to either display all incoming email in plain text format, or ensure that HTML email is opened in the Restricted sites security zone.
- Ensure that antivirus software is up to date. Symantec now has definitions that catch this malware.
- Always execute browser software as a user with minimal system privileges.
A spokesman for RealNetworks, maker of RealPlayer, told eWEEK that the company is currently investigating the vulnerability. He had no timeline for when a patch would be issued.
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