Bitcoin Mining

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Hack "750x7" - Technical Details for Detection & Recovery

Synopsis

Attackers enter linux machines by means of IPMI or RFB console access, install a rootkit and launch a bitcoin miner. Additional functions may include: distribution of Hacking/Mining software, attacking other machines, possibly stealing passwords.

About

This writeup sums up what ACOnet-CERT has learnt during the investigation of an incident. It turned out that many machines were involved, so we set up this page in the hope it will be useful. It aims at helping sysadmins and security teams to

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This writeup refers to one particular campaign, which may or may not correspond to anyones particular situation. Please keep also in mind that the attackers are likely to change their methodology at some point in time, i.e. what's written on this page will become outdated sooner or later. We welcome feedback and updates though (preferably by mail to cert@aco.net).

Distribution Distribution on a "need to know" basis is fine with us. It is recommended to simply pass on a link to this page, so that updates can reach the persons involved. Please don't link prominently to this page on a public web site. 

Thanks: We would like to thank all those people who have shared their knowledge with us and have provided important hints which helped us a lot in our own work. 

Disclaimer: Any information on this page is provided without warranty, may contain errors, misunderstandings and can be misleading, obsolete or otherwise inaccurate. In no way may ACOnet or the University of Vienna be held liable for damages or whatever can cause liability in which jurisdiction ever.

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Indicators of Compromise

The following IOCs have been observed on machines involved in the "750x7" hack, but may also 

Network

• Traffic to 119.78.232.8. This is the bitcoin master server at the time of this writing.
• Inbound ssh connections that can't be attributed to legitimate users.
• Possibly outgoing scanning activity, in particular for port 623 and 5900.
  
  

• Unexplained reboots

Intrusion

As far as we could observe, the attackers intrude the system in one of at least two, possibly three ways:

• IPMI (remote management as in e.g. ILO, DRAC etc, port 623 tcp/udp). This protocol has severe weaknesses which, if not properly mitigated, would allow an attacker to reboot the machine into a live linux image. He would then mount the root disk, alter it (thereby circumventing any of the target system's security controls), and then reboot the compromised system.
• RFB (remote framebuffer as in e.g. VNC). We currently have no information on how exactly the attackers exploit this protocol, but they are actively scanning for it.
• Possibly by using compromised accounts. We observed that an ssh client was dropped in /usr/local/bin. Though we haven't analysed it, chances are that this binary collects the user's passwords as they log into other machines from the compromised one.

FAQ

Q: What does the name 750x7 stand for?

A.: Nothing in particular. We felt it necessary to clearly distinguish this case/pattern from others like, for instance, the bitcoin mining malware for windoes that was found a couple of years ago. Since the attack we investigated had no outstanding characteristics, we couldn't figure out an obvious name. Eventually, we went for an "opaque character string".