Attackers are exploiting a zero-day vulnerability in RealPlayer in order to infect Windows machines running Internet Explorer, Symantec said late last week. The security company issued an alert that rated the threat with its highest possible score.
According to a warning issued to customers of its DeepSight threat network, Symantec said an ActiveX control installed by RealNetworks' RealPlayer program is flawed. When combined with Microsoft's Internet Explorer (IE) browser -- which relies on ActiveX controls to extend its functionality -- the bug can be exploited and malicious code downloaded to any PC that wanders to a specially crafted site.
Only systems on which both RealPlayer and IE have been installed are vulnerable.
Symantec ranked the attack as a "10" on its urgency scale because it has confirmed that attacks are being conducted in the wild; those attacks have resulted in malicious code downloaded to victimized PCs. The only bright spot: "We are not currently aware of widespread exploitation of this issue," the company's warning read. In another section of the advisory, it listed just two IP addresses that it has found hosting exploits of the RealPlayer bug.
Multiple versions of RealPlayer install the ActiveX control, including the current 10.5 and the beta of Version 11. RealNetworks has not released a fix, but Symantec said it had informed the media player's maker of the bug.
"Attacks that exploit this issue may get delivered to a victim through various means, most typically, though, this style of attack is carried out through malicious Web content," said Symantec. "For example, the exploit could be embedded in the HTML of advertisements that are published on trusted Web sites, or could be embedded as an IFrame in a compromised Web domain."
Symantec also referenced a blog that had posted some information about the RealPlayer vulnerability. The blogger, identified only as Roger, claimed that the NASA space agency has warned workers not to use IE because of an unspecified problem with RealPlayer.
Roger quoted from what he claimed was a NASA bulletin. "The malware appears to be spreading through a large variety of common and highly-respected Internet sites," the NASA warning reportedly said. "However it does not appear these sites are themselves infected. The affected sites are serving solely as a mechanism to attract potential victims." NASA's public affairs team at the Ames Research Center in northern California was not available for comment.
Until RealNetworks releases a patch, Symantec said the best advice it can give is to disable the vulnerable ActiveX control by setting its "kill bit." To do that, however, requires editing the Windows registry, a task most users shy away from.
More information will be posted to this page on the SecurityFocus Web site, which Symantec operates, when it is available.
RealNetworks was not available to answer questions about when it would patch the player or whether it would issue an advisory of its own.