Microsoft warned last week that it would be easy for cybercriminals to build new attacks using bugs it patched in the Internet Explorer browser; now that prediction has come true.
Microsoft has said that either of these vulnerabilities would be easy to exploit in online attacks.
Over the weekend, Trend Micro researchers spotted what appears to be a small-scale, targeted attack that exploits the flaw to install spy software, said Paul Ferguson, a researcher with the antivirus vendor.
"It installs a back door that uploads stolen information on port 443 to another site in China," he said.
Microsoft was unable to immediately comment on Trend Micro's report on Tuesday.
Although Ferguson does not know who wrote the attack code, he said that it looks similar to software that was sent to pro-Tibetan groups about a year ago, apparently for the purpose of intelligence gathering.
Both last year's attack and this latest malware are triggered when the user opens a malicious Word document. That document contains an ActiveX object that connects IE to a malicious Web site, which launches the attack and then installs the spy software.
The criminals don't need to use Word to exploit this flaw - the attack would work if the victim were simply tricked into visiting a malicious Web site - but this technique is consistent with past Tibet-focused attacks, Ferguson said.
Whether this will lead to more widespread Internet Explorer attacks is unclear, Ferguson said.
Verisign's iDefense group thinks that more attacks are likely.
"Although this attack is limited in scope and will likely only be targeted to very few organizations, the availability of reliable exploit code will soon be discovered by others and these attacks will likely be widespread within a week's time," the company said in an alert sent out to customers on Tuesday.
"Right now, we don't see any real proof of an ongoing campaign here," Ferguson said. "But ... it's very simple to mitigate this threat completely. You don't have to worry about antivirus protection: Just patch your machines."