Late last year, Facebook partnered with IT security vendor ESET to provide a free and basic anti-malware program to users. If you log on to Facebook with a device that’s infected with malware, a message will appear offering you the chance to scan your device and remove the bug—all without leaving Facebook. It’s a pretty helpful feature, though it’s one that can seem too good to be true. Indeed, one blogger recently wrote about his experience believing that the tool was, itself, malware.

“I spent quite some time researching this on the Internet as I had not heard of this ESET Online Scanner before,” Romona Foster wrote. “What I mostly found online were people asking if it was really Facebook or some malicious virus that was causing this, which was my concern. I also found a lot of people who were cursing Facebook for putting them through this daunting process.”

At first glance, the tool does look like malware. A pop-up box loudly trumpets that “Your Computer Needs to Be Cleaned,” and then offers users a chance to fix the problem. However, it is a genuine feature that is both helpful and free. Still, it’s a good idea to be skeptical of offers like this when you see them on Facebook. While ESET is real, many similar “tools” are not.