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Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

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Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#31

> Note: successful exploitation does not generate any log entries. Does this mean, had this exploit gone unnoticed, the attacker could have executed arbitrary commands as root without even a single sshd log entry on the compromised host regarding the 'connection'?

Yes.. The RCE happens at the connection stage before anything is logged.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#33

It's pretty interesting that they didn't just introduce an RCE that anyone can exploit, it requires the attacker's private key. It's ironically a very security conscious vulnerability.

For real, it's almost like a state-sponsored exploit. It's crafted and executed incredibly well, the performance issue feels like pure luck it got found.

Do we have a detailed technical analysis of the code? I read a few analysis but they all seem preliminary. It is very useful to learn from the code.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#35
post #30

Do we know if this exploit only did something if a SSH connection was made? There's a list of strings from it on Github that includes "DISPLAY" and "WAYLAND_DISPLAY": https://gist.github.com/q3k/af3d93b6a1f399de28fe194add452d01 These don't have any obvious connection to SSH, so maybe it did things even if there was no connection. This could be important to people who ran the code but never exposed their SSH server to…

Could that be related x11 session forwarding (common security hole on the connectors' side if they don't turn it off when connecting to an untrusted machine).

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#36
Stuff like this is why I like port knocking, and limiting access to specific client IPs/networks when possible.

20 years ago, I was working at an ISP/Telco and one of our vendors had a permanent admin account hardcoded on their gear, you couldn't change the password and it didn't log access, or show up as an active user session.

Always limit traffic to just what is necessary, does the entire internet really need to be able to SSH to your box?

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#38

It's pretty interesting that they didn't just introduce an RCE that anyone can exploit, it requires the attacker's private key. It's ironically a very security conscious vulnerability.

For real, it's almost like a state-sponsored exploit. It's crafted and executed incredibly well, the performance issue feels like pure luck it got found.

I like the theory that actually, it wasn’t luck but was picked up on by detection tools of a large entity (Google / Microsoft / NSA / whatever), and they’re just presenting the story like this to keep their detection methods a secret. It’s what I would do.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#39

Imagine how frustrating it has to be for the attacker to meticulously plan and execute this and get foiled so late in the game, and so publicly

Must be punching the air right now

Likely a team of people at a three letter agency.
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