Flaws in ActiveX controls are being increasingly used to run security exploits.

Arbitrary file overwrite and deletion flaws, typically exploited through ActiveX controls, are well on the way to becoming a new class of security flaw, according to net security firm Symantec.

"These vulnerabilities exist particularly because of a registered ActiveX control failing to restrict which domains may load the control for execution. An attack exploiting this vulnerability can lead to arbitrary code execution by a remote attacker," a blog posting by Symantec researcher Parveen Vashishtha warns.

Since May, Symantec has logged 40 vulnerabilities of this type in applications from vendors including VMware, Microsoft Visual Studio, NCTSoft, and HP Photo Digital Imaging. The flaws are easy enough to exploit. The approach also carries additional benefits for hackers.

For example, a malicious payload of a batch file may come enclosed within a signed ActiveX control, which means that user intervention to approve the actions of a malicious payload may not be required. Typical exploitation scenarios include tricking a user into visiting a maliciously-controlled website.

Fortunately, by default, Internet Explorer blocks ActiveX controls. But consumers should be wary about allowing anything except trusted ActiveX controls. Third-party security products can also defend again the threat, which is explained in greater depth in a posting by Symantec here (http://www.symantec.com/enterprise/security_response/weblog/2007/10/activex_file_overwritedelete_v.html). ®

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