Researchers observed an attack campaign distributing fake browser updates to infect website visitors with ransomware and banking malware.

Sucuri reported that the attackers inject either links to an external script or the entire script code into a compromised webpage. In both cases, this code creates a message box informing the user that a critical error resulted from an outdated version of the web browser. It then prompts the visitor to update his or her browser version while displaying garbled text in the background to legitimize the appearance of a critical browser vulnerability.

If the user clicks the “Update” button within the message box, the computer downloads a ZIP archive. This resource harbors a JavaScript file with a name that mentions “browser” and “components,” an apparent attempt to further convince the user that it is legitimate.

Once run, the file tries to download browser.jpg, which is actually a Windows EXE file containing ransomware. By comparison, the Android version of this campaign downloads banking malware onto the infected device.

A Long History of Fake Browser Updates

The tactic of using fake browser updates to deliver malware goes back to at least 2012, when Trend Micro discovered several websites offering fake, malware-laden updates for popular web browsers. A year later, ThreatTrack Security Labs came across fake upgrades hosted on an online repository.

The tactic has also been active in recent years. In 2017, for example, Proofpoint discovered a malvertising attack that used fake browser updates to deliver the Kovter ad fraud malware. Malwarebytes Labs came across something similar when it uncovered the FakeUpdates malware campaign in November 2018.

How to Defend Against Banking Malware and Ransomware

Security professionals can help defend against banking malware and ransomware by taking a risk-based approach to patch management, which can help them decide whether to patch known component vulnerabilities or replace at-risk items with more secure ones. Security teams should also invest in a solution that delivers phishing intelligence about ongoing attack campaigns, which helps responders determine which indicators pose the greatest risk to the organization’s environment.