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Trojanized SSH Daemon In the Wild, Sending Passwords To Iceland
An anonymous reader writes "It is no secret that SSH binaries can be backdoored. It is nonetheless interesting to see analysis of real cases where a trojanized version of the daemon are found in the wild. In this case, the binary not only lets the attacker log onto the server if he has a hardcoded password, the attacker is also granted access if he/she has the right SSH key. The backdoor also logs all username and passwords to exfiltrate them to a server hosted in Iceland."
Would one of the 320k icelanders please stand up and make it known who decided to do this. I mean come on this country is smaller than most cities people know. I bet they find out who dun it right quick.
Somebody had to say it.
I have something in common with Stephen Hawking...
I'd think this was a story about Cisco gear from not that long ago.
#DeleteChrome
So being compromised is the first condition to get "infected"? I'd say it's a non-issue, although it's always better to be acknowledged.
Please don't misuse silly words like exfiltrate because it sounds cool. You know, like saying it was cloud crowd sourced in the third inning of the ether space. It makes no sense in your context and your have blown all credibility in this story. You can replace "exfiltrate" (omg so cool) with "send" (omg..oh, so simple!).
I cleaned up an a backdoored Debian system after discovering md5 sum mismatches on all the ssh binaries from the original packages some time ago.
debsums is a nice utility to check this for you, granted that the attackers didn't modify the signing keys and installed their own package.
I always post my passwords at linuxrepository.org with our without a trojaned sshd
I myself have set up modified versions of the sshd dameon/ssh client on various rooted machines in the past (mine was simply allowing root login without logging anything with a hardcoded password + writing logins/hosts/passwords, after encryption, deep inside a fake shared library on the system - this took less than an hour to implement in the openssh source).
In all cases, despite the extreme simplicity of this mechanism, it was very, very easy to then gain access to a lot of other boxes on the network, and eventually to all the network itself. Just wait for the clueless sysadmin to log in (dumping his pass), then wait for him to use ssh to log in to another box in the network (dumping his pass as well). Then install the modified version of the daemon/client on to this new box. Rince, repeat.
It is in a way terrifying to see how most sysadmins are clueless. So, IMHO, a few measures that should be compulsory on any network:
- Do not allow write access to any essential binaries (like sshd, ls, and so on). If you have to, make sure you have a stealthy daemon checking the hashes of all critical binaries at regular intervals to make sure they have not been tampered with. ...there are also other ways to implement an effective kernelspace rootkit, like VFS hijacking, so make sure you disable modules loading in the kernel before compiling (and check the hash of the kernel image itself regularly as well).
- Never, ever, log in to a server in your network from another server in the same network. Use port redirection, then log in from your initial box.
- Always use a dedicated server for system logs (syslog handles that very easily - sending logs over the network). That way, the logs of the initial system compromise will not be deletable. Do not ever log in remotely to this dedicated machine.
- After the initial system install, make a dump of the syscalls table of your kernel. Check it regularly to make sure it has not been tampered with (kernelspace rootkits usually hijack this table).
-
Those are the main sane measures that come to mind (this is all based on real life experience intruding into large companies/laboratories/university systems, without ever having been detected). Posting anonymously for obvious reasons.
The article says "...discovered on compromised servers."
If they are not distro(i.e. ubuntu, redhat,centos, etc.) servers, or openssh servers, this is a non-story. I can create a random domain, compile a version of openssh to sends passwords to me and host it on my server as an official ssh binary.
If I install stock wordpress with access to the file, would that then count a compromised?
It seems odd to me that a recent /. article (read link in summary) also mentioned XOR style code that could identify the SQL Slammer perpetrator. It could just be coincidence... but the same guy that made this tojanized version of SSH could also be the same guy that made SQL Slammer. Both have an infatuation for XOR. Both Trojan and Slammer are sexual terms. SSH, SQL, and XOR are 3 letter-abbreviations. Conspiracy! 3^3^3=3! And it is the year 2013! OMGZ! Ahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh! This was also posted by timothy. Arrest TIM O THY!
The G
This makes no sense. Once somebody has root and can write to those binaries you are already fucked and they can change access to anything they like, and then write over it to their hearts content.
Putting them on read only media sounds like a cool idea but is difficult to implement for anything other than the short term and can be circumvented if somebody roots your box anyway. There's the script kiddie toy of changing file attributes (and thus announcing to people that they've been rooted) which this AC may think is some sort of real security measure if sysadmins use it, but that's merely annoying to anyone that has root and isn't going to slow down even a newbie with access to google.
Apparently it's quite common for attackers to actually patch the security holes they used to get in, once they've installed their backdoors. Don't want someone else getting in the same way, after all...
Personally I think a password is a very good idea if combined with a key. If a laptop gets stolen the thief can log in directly with the stolen key saved on the laptop. If they have to work out a password as well they only get what is on the laptop.
I never use passwords with ssh. If ssh asks me for a password, I know something is wrong. I made this policy decision because of the endless attempts to log into my machine from all over the world. It was either something like a yubikey, or only using public key authentication. I went for the public key authentication.
Need a Python, C++, Unix, Linux develop
Obligatory.
Except how will you know it's compromised unless you're scanning from a clean system/media?
You *could* have another machine pop in and compare md5's or whatever, but that assumes that "md5sum" and a bunch of others machine being tested isn't compromised.
You *could* also run the SSH'able machine inside a VM and check from the VM host, but the host could still be compromised or other issues.
Another option is to routinely check by booting from secure media, but that involves downtime.
Investigating a compromised system is one thing. I believe the GP was more about discovering that the system is compromised in the first place.
fail2ban solves the remote login attempts.
I only install from sources you insensitive clod!
Or you could source two binaries from two diff repo servers in two diff countries, and only accept the install if they both are identical.
Liberty freedom are no1, not dicks in suits.
If they installed a java version of SSH, it would be ultra secure, but you need 750meg of ram for each ssh session.
Go Oracle, Larry is elite.
Liberty freedom are no1, not dicks in suits.
Man, you would run md5sum on the actual compromised box??
Why not do it from a ISO booted linux, and nfs share the whole box , so you can sum it from the outside.
What you really need is all binaryies libs running of a partition that is read only. Kind of like android.
Liberty freedom are no1, not dicks in suits.
No hacker can find the binaries to a PPC mac os 10.5
Duh, you can boot OSX from a DVD, if you are really that paranoid.
Liberty freedom are no1, not dicks in suits.
woooosh!
They have thousand of eyes looking at the source and working on ways to improve things. What are the Window's folks doing?
Time is what keeps everything from happening all at once.
I may have missed it but was this a binary package for a specific distro (on their own servers) or a binary on an untrusted server not attached to any specific distro?
Unless you're auditing said sources, you're no better off than installing binaries.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
Because the source server that feeds both could NEVER be compromised.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
Unless you're auditing said sources, you're no better off than installing binaries.
You know that Gentoo checks the SHA256 SHA512 and WHIRLPOOL digests of the downloaded sources before compiling right? You also know that the digests stored in Gentoo's repository are signed using a PGP key of the package maintainer, right?
So can you please explain me again why I need to audit such sources? Sure sources can be compromised at upstream's servers and Gentoo maintainers can also make mistakes but this is not what TFA is about.
You'd like to think so, but when things like this happen, you can see that having thousands of unqualified people looking at code and sometimes modifying it is not really any benefit to security at all.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
That's why ssh is trojaned - it's how they got in. Once they get into one box some other way, the trojan gets them into every box a user connects to via ssh. So it spreads like a virus. At some point, an admin with access to a lot of machines, like a hosting company admin, uses ssh to rsync / scp to their main machine. Then the bad guys get access to every machine hosted there.
Yes cause we all know how secure and well coded java apps are.
I am Bennett Haselton! I am Bennett Haselton!
If binaries are signed the same way, then there is no security advantage in compiling from source.
All the machines I cleaned up got hacked due to some wise guys who thought that using 4 letter passwords were kewl.
Machines? Multiple?
My real question is; how was it determined that they were compromised and what made you look for the compromise in the first place?
That's all well and good, if your attackers are lazy. But with the advent of SSL VPNs and call-out or reverse connection technology like GoToMyPC, all you see on the wire is an HTTP or HTTPS session. Nothing suspicious, except that it's a tunnel into your network from Latvia.
I think the days of just looking for an IRC connection or non-standard port are gone.
Aw, I don't know why you were modded troll. That's funny. :)
And only ultra secure because it would work for a few days, and then hang, refusing all access. :)
Serious? Seriousness is well above my pay grade.
Hands up for everyone that has a prerooted md5sum of their /bin and /sbin directory files for everyone of their machines. How about for just supercritical machines? How about for all files and dirs?
I'll wager that 0.001% have any such listing. I've yet to see anyone even claim to have such a listing. So, I'm regarding all this expert talk in this thread as 100% BS.
How is trusting the signature on source files different from trusting signed binaries?
All binaries in Debian are cryptographically signed, and the package manager will not install a package that doesn't match the correct signature unless you override the checks.
You can audit your system at any time with debsums to find any binaries and config files that differ from the official versions.
I think the level of trust is pretty close to the same, so unless you are auditing the sources, you are in pretty much the same position as trusting the hashes in binary packages. You could be worse off if it is your compiler that has been trojaned ;)
Everyone replying here seems to be obsessed in comparing binary vs source and totally miss the point. The point is that
Gentoo users do not have the habit of installing binary packages at all, for that reason this trojanized sshd BINARY does not concern us.
Wooooooosh!
if you have your servers compromised, the data on them, and login attempt into them may be keylogged, WOW! Is this the level of articles we want on slashdot ?
You are completely missing the point. The point is that there is no difference between running untrusted binaries and compiling and running from untrusted source.
Since Debian (and most other distributions) check the digests of binaries this trojan doesn't concern us. Gentoo doesn't really have a special position in this case.
Wooooooosh!
I'm not splitting hairs because ssh login with a key and no pass phrase is a frequent shortcut.
You don't know what he's talking about either - you are just adding things you think should be there but are not.. I'm making a comment on something that should be there if it's going to be good advice but is not, even if it was intended - neither of us know do we?
The trojaned ssh isn't the one installed from the repo, it's installed later by the bad guy, so it doesn't matter how you installed . Again, the trojaned ssh isn't the one you installed. The ONLY difference between source vs. binary packages in this case is that people who installed binaries could be alerted that the hash of the existing file doesn't match the correct binary. So binary installs are SAFER as far as this trojan.
How does the bad guy get the trojan on your system, if not from the repo, you ask? He gets access when someone else who is infected logs into your machine - your sysadmin, your hosting company, a vendor, etc.
The bad guys only had to compromise one machine, then the trojan spreads. Say for example my co-worker Jeff has him home machine infected. He uses ssh to connect from home to his office. The bad guys now haveaccess to infect his office machine. Jeff is a sysadmin at the office, so from his office desktop he logs into various servers. That spreads the infection to the servers. I then use scp (ssh file copy) to pull some files on to a server from my work desktop. Now my desktop is infected. Later, I ssh from work to my home office. Now my home office is infected.
For this reason, we have a rule. Always ssh FROM the more trusted machine TO the less trusted one, never the other way around. For scp and rsync, that means always PUSH files to a client's machine or any server on the public internet, never PULL to a less trusted machine from a more trusted one.
How does the bad guy get the trojan on your system, if not from the repo, you ask? He gets access when someone else who is infected logs into your machine - your sysadmin, your hosting company, a vendor, etc.
Dude, this does not make any sense at all!
If person X logs into my machine (which is not infected) and that X is infected with the trojanized daemon. Then the attacker will not be able to find out the X's account password in my machine because the connection was made to my uninfected daemon and not to X's infected daemon. Get it?
For this reason, we have a rule. Always ssh FROM the more trusted machine TO the less trusted one, never the other way around. For scp and rsync, that means always PUSH files to a client's machine or any server on the public internet, never PULL to a less trusted machine from a more trusted one.
How would that work? Honestly I don't know so don't troll me ;P. How would I connect to my local ssh server from a work resource (that uses rsa key concatination), from my house?
It would be nice if ssh could enforce this and refuse to connect if you try to break the policy.
Yeah, and other operating systems do hashes for their binaries, too.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
Also, even compiling from trusted source is no good if your compiler is compromised.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
You know that Gentoo checks the SHA256 SHA512 and WHIRLPOOL digests of the downloaded sources before compiling right? You also know that the digests stored in Gentoo's repository are signed using a PGP key of the package maintainer, right?
Yes, but if you are hosting the sources, you also control whatever checksum also appears on your website.
Besides, hosting precompiled Windows binaries is a great way to trick lazy admins. First, a lot of open-source hosts / projects do not provide easy access to Windows binaries, and many admins don't have compilers (they don't program and so consider compiling out of their job description), and finally since there really is no automated way to check the checksums they avoid doing it. (Though automating checking MD5's etc. would obviate using them in the first place) So it's just easier to trust a host with their binaries.
Of course all this could be avoided by using only trusted sources. But I said they were lazy, not smart.
THINK! It's patriotic
He's saying the guy uses some zero-day exploit to penitrate your system, then installs the trojan as admin, edits the logs, and disappears from your system. Vala! Infectecado!
Hopefully your AV will catch it in a few days as the exploit is discovered elseware on the net. Though it could take longer if he is only installing them by hand.
THINK! It's patriotic
Get it?
No. :)
If you replace the daemon binary then wouldn't it make sense to replace a few client binaries as well?