Hackers are trying to dupe people into downloading malicious software labeled as Adobe Systems' Flash Player, prompting a warning from the company.

Adobe is advising users to ignore links on social-networking sites that lead to other Web sites purportedly hosting Flash Player, as those sites often have malicious software.

"If the download is from an unfamiliar URL or an IP address, you should be suspicious," Adobe's advisory said.

Labeling malware as legitimate software is an old social-engineering tactic. But given the wide use of Flash on Web sites, most people have installed Flash Player to display the content.

Adobe has also updated Flash Player several times this year due to other security issues, so it may not come as a surprise to see an upgrade message, albeit a fake one. The current version is 9.0.124.0.

Adobe said the Flash Player available on its Web site is digitally signed and validated by the Windows OS during an installation. Users can also verify that the Flash Player installer is legitimate by right-clicking on it, selecting "properties" and going to the "digital signatures" tab. It should say that the publisher is "Adobe Systems, Incorporated."

Security vendor Kaspersky Lab wrote on Monday that the micro-blogging site Twitter was being used for attacks employing the Flash Player ruse.

A Portuguese-language profile was created that included a link to a video that, if clicked, starts downloading what is supposed to be Flash Player. Instead, 10 varieties of malware that steal banking-related information are dumped on a PC.

The IDG News Service is a Network World affiliate.