Malicious attackers have used the leaked source code of a popular remote access tool for Windows, known as Ammyy Admin, to create a remote access trojan which researchers at security firm Proofpoint have dubbed FlawedAmmyy.
The RAT is being used to gain access to victims' machines, steal files and also credentials and has been in use since the beginning of 2106, the researchers said.
FlawedAmmyy was seen recently in massive email campaigns on 5 and 6 March, and was the second-stage download in the campaign that began with the sending of messages containing zipped .url attachments.
On 5 March, messages were sent from addresses that spoofed the recipient's own domain, with subject lines indicating that the message had a receipt as attachment.
{loadposition sam08}These .url files are interpreted by Windows as Internet shortcut files but because they begin with a "file://" patch, they end with the downloading and execution of a JavaScript file over the SMB protocol.
The JavaScript file, in turn, when executed, brings in the trojan downloader Quant Loader; this then fetches the FlawedAmmyy RAT.
The RAT has all the functionality of the original, legit software; it can do remote desktop control, act as a file system manager, provide proxy support and also allows audio chat.