{"id":80813,"date":"2018-03-13T15:27:06","date_gmt":"2018-03-13T22:27:06","guid":{"rendered":"https:\/\/cloudblogs.microsoft.com\/microsoftsecure\/?p=80813"},"modified":"2023-05-16T13:53:32","modified_gmt":"2023-05-16T20:53:32","slug":"poisoned-peer-to-peer-app-kicked-off-dofoil-coin-miner-outbreak","status":"publish","type":"post","link":"https:\/\/www.microsoft.com\/en-us\/security\/blog\/2018\/03\/13\/poisoned-peer-to-peer-app-kicked-off-dofoil-coin-miner-outbreak\/","title":{"rendered":"Poisoned peer-to-peer app kicked off Dofoil coin miner outbreak"},"content":{"rendered":"

On March 7, we reported that a massive Dofoil campaign<\/a> attempted to install malicious cryptocurrency miners<\/a> on hundreds of thousands of computers. Windows Defender Antivirus, with its behavior monitoring, machine learning technologies, and layered approach to security<\/a> detected and blocked the attack within milliseconds. Windows 10 S<\/a>, a special configuration of Windows 10 providing Microsoft-verified security, was not vulnerable to this attack.<\/p>\n

A new capability in Windows Defender AV, Emergency Dynamic Intelligence Update (EDIU), helped push protections from the cloud directly to endpoints within 15 minutes after the outbreak was identified. This feature, currently in preview, is designed specifically for these kinds of outbreaks and delivers protections in near real time. In addition, client endpoints automatically downloaded definition packages (VDM) from Windows SUS servers and Microsoft Update servers.*<\/p>\n

Immediately upon discovering the attack, we looked into the source of the huge volume of infection attempts. Traditionally, Dofoil<\/a> (also known as Smoke Loader) is distributed in multiple ways, including spam email and exploit kits. In the outbreak, which began in March 6, a pattern stood out: most of the malicious files were written by a process called mediaget.exe<\/em>.<\/p>\n

This process is related to MediaGet, a BitTorrent client that we classify as potentially unwanted application (PUA)<\/a>. MediaGet is often used by people looking to download programs or media from websites with dubious reputation. Downloading through peer-to-peer file-sharing apps like this can increase the risk of downloading malware.<\/p>\n

During the outbreak, however, Dofoil didn\u2019t seem to be coming from torrent downloads. We didn\u2019t see similar patterns in other file-sharing apps. The process mediaget.exe always wrote the Dofoil samples to the %TEMP% folder using the file name my.dat. The most common source of infection was the file %LOCALAPPDATA%\\MediaGet2\\mediaget.exe<\/em> (SHA-1: 3e0ccd9fa0a5c40c2abb40ed6730556e3d36af3c<\/em>).<\/p>\n

Recommended reading: <\/strong>For campaign statistics, payload details, and the Windows Defender response, read:<\/p>\n