Cybercriminals have devised a new method of delivering cryptocurrency mining malware by exploiting email auto-replies, according to a recent report by Russian cybersecurity firm F.A.C.C.T. In this campaign, hackers compromised email accounts and set up seemingly innocent auto-reply messages containing malicious links that would download the Xmrig crypto-miner, a popular tool used to mine the cryptocurrency Monero (XMR).
The attack primarily targeted employees at Russian tech companies, retail marketplaces, insurance firms, and financial institutions. F.A.C.C.T. researchers identified approximately 150 emails laced with the Xmrig crypto-miner since the end of May.
What makes this tactic particularly dangerous is that the potential victims initiate the communication. Unlike traditional phishing or mass email scams, where recipients can more easily detect and ignore suspicious messages, these malicious auto-replies appear more legitimate since they are in response to an email the victim has already sent.
“This method of malware delivery is dangerous because the potential victim initiates communication first,” said Dmitry Eremenko, senior analyst at F.A.C.C.T. “This is the main difference from traditional mass mailings, where the recipient often receives an irrelevant email and ignores it.”
The Xmrig Crypto-Miner: A Persistent Threat
Xmrig is an open-source cryptocurrency mining software commonly used to mine Monero, a cryptocurrency favored by cybercriminals for its enhanced privacy features. Over the years, hackers have continued to evolve their methods to covertly deliver Xmrig to victims. For example, one recent campaign used pirated versions of Apple’s Final Cut Pro to install the miner on unsuspecting users’ computers.
While F.A.C.C.T. did not disclose specific details about the success of the latest attacks or identify those responsible, the firm noted that all compromised email accounts had previously had their credentials leaked on the darknet, along with personal data. The affected accounts belonged to a range of businesses, including small trading firms, construction companies, a furniture factory, and even a farm.
A Growing Cybersecurity Threat
The use of auto-replies to deliver malware represents a new frontier in social engineering tactics. As hackers continue to refine their methods, organizations must remain vigilant and take extra precautions to secure their email systems and prevent account compromises. The incident underscores the importance of regular security audits, monitoring for credential leaks, and educating employees about the risks of seemingly harmless email interactions.

