{"id":76061,"date":"2014-12-17T16:20:26","date_gmt":"2014-12-18T00:20:26","guid":{"rendered":"https:\/\/cloudblogs.microsoft.com\/microsoftsecure\/?p=76061"},"modified":"2023-05-15T23:13:14","modified_gmt":"2023-05-16T06:13:14","slug":"your-browser-is-not-locked","status":"publish","type":"post","link":"https:\/\/www.microsoft.com\/en-us\/security\/blog\/2014\/12\/17\/your-browser-is-not-locked\/","title":{"rendered":"Your Browser is (not) Locked"},"content":{"rendered":"

Most ransomware has a binary file that needs to be executed before it can infect your PC. Ransomware usually relies on social engineering or exploits to infect unsuspecting users. However, some malware authors are bypassing this requirement with a new trick – browser lockers.<\/p>\n

Unlike traditional ransomware threats that lock the entire desktop, browser lockers only lock the web browser of an infected PC. Most other malware needs a user (or other malware) to manually run it. Browser lockers don\u2019t need to be manually run, they don\u2019t have a binary file and they are mostly written in JavaScript. The script runs in the web browser and its main purpose is to disable any form of action that can close the browser – such as clicking the close button and pressing certain shortcut keys (for example, Alt + F4). All attempts to close the browser will result in a warning message box, an example is shown in Figure 4.<\/p>\n

Microsoft detects browser locker malware as Ransom:JS\/Brolo<\/a> and Ransom:JS\/Krypterade<\/a>. The graphs below show the number of encounters and countries affected by these threats in recent months.<\/p>\n

These threats run when a user is redirected to a malicious URL. Although a user might visit a clean domain or website, they can be redirected to a malicious URL instead via pop-up ads.<\/p>\n

Once redirected to the browser locker landing page, a visible lock screen is displayed through the browser. At this point all attempts to close the browser are futile without the help of another application.<\/p>\n

An example of a Ransom:JS\/Brolo browser lock screen is shown below. The message differs from browser to browser, and can be region-specific.<\/p>\n

Each browser locker may have a slightly different appearance, with changes to the images and messages. However, they usually try similar scare tactics:<\/p>\n