What’s the worst case scenario for browser malware? A number of nightmare scenarios come to mind: keylogged credentials, ransomware or hidden background downloads of more malicious programs. As reported by PCWorld, however, cybercriminals have now upped the ante with a kind of Chrome chameleon called eFast that’s able to hide in plain sight by installing and then running itself in place of the popular Google browser. Everything looks familiar but performs just a bit differently, potentially with constant pop-ups and search ads. Here’s how to spot this doppelgänger in the wild — and how to show it the door.

Nothing to See Here — Except Malware

Browser malware has become big business over the last few years as attackers look for ways to tap the vast number of users leveraging Chrome, Internet Explorer, Firefox and other offerings to shop online, connect with friends and even conduct financial transactions. Historically, malicious browser code focused on adding something to existing software and hoping users won’t immediately notice.

To make things more difficult, cybercriminals hid this malware behind legitimate-sounding file names and buried it in out-of-the-way directories. But browser-makers are getting better at sniffing out infected code before it sets up shop both by using active detection technologies and giving users granular control over which (if any) extensions run during browser sessions.

The creators of eFast decided to vault over this security hurdle by creating a piece of software that installs itself in place of Chrome, then replaces all shortcuts and links to the legitimate Chrome browser with ones that look almost identical. As noted by The Hacker News, eFast also attempts to delete Chrome altogether and changes both file and URL associations to ensure virtually any file or process call causes the fake browser to open.

Once up and running, eFast generates constant pop-up content, layers advertisements on top of Web pages, redirects users to sites containing malicious content and tracks user movements across the Web. In effect, the fake browser uses every play in the Web malware book to ruin the browsing experience. And since the code isn’t part of Chrome but an entirely separate entity, eFast is getting away with it.

Binning the Browser

So how do users know they’re infected? Tech-savvy netizens may notice that the Chrome icon looks a little off, but surefire signs include massive pop-up volumes and website redirections. The real telltale, however, is that no malicious extensions will show up in Chrome’s advanced settings despite this odd behavior. Even then, some users may attribute the problem to specific websites or services because the fake looks so convincing — the excellent disguise is thanks to Google’s open-source Chromium software, which allowed the eFast creators to fashion a near-perfect replica.

Fortunately, dealing with the doppelgänger isn’t terribly difficult. Best case? Users don’t download any third-party content in the first place, meaning their systems are never infected. If eFast has taken over, however, the first thing to do is stay out of Chrome since there’s nothing here but smoke and mirrors. Instead, users should head to the Programs and Features section of the Windows Control Panel or locate the Applications folder in their Mac Finder. Typically, the program is properly labeled as eFast, but also conduct a by-date search to see exactly what’s been installed and when, and get rid of the malicious program. Finally, download a fresh copy of Chrome.

Malware-makers are getting smarter: Instead of infecting browsers, the new attack vector is total replacement, giving them total control. Keep an eye out for this Chrome chameleon, and if spotted, bin it as soon as possible.