As a security guy I find my paranoia levels are slightly high than most, a little something inside me picks up on things that general users miss that indicate that something isn’t right. This morning was no exception….
After acquiring coffee, morning inbox was opened which presented the following:
These are email alerts sent by the monitoring system Nagios, running within InfoSanity’ networks. The NRPE-check_users parameters have been modified from the Debian defaults to be more paranoid; triggering a warning alert with a single user logged into the server, and go critical if more than one. So; from this, someone is logged into the web server, and it isn’t me.
Feeling the onrush of panic, I log into server and chuck commands at a shell to see who is violating my system. Last, who and /var/log/auth all showed that no one had accessed the server at the time of my alerts. Everything good? Not if your paranoid, starting to smell a rootkit causing the system to lie to me.
There are a couple of anti-rootkit utilities that have served me well in the past, chkrootkit and rkhunter. Wondering which one to run? As we’ve already discovered I’m paranoid, answer was both. And both gave a clean bill of health to the system. Now I’m really getting paranoid.
Wanting to see if I’ve missed a trend, or if the issue is present with other servers in the environment I log into Nagios interface for a more detailed look, and find the answer:
Anyone spotted it? Yep, the service alert went critical when the check’s socket timed out (network issue), and then dropped to warning showing a single user when the connectivity returned; which was correct, I’d forgotten to log out of the console on my last VMWare connection. Stepping down from high alert…..
Morale of the story?
Don’t respond to system alerts before finishing first coffee of the morning. The events weren’t a total loss though, besides getting my heart-rate up and blood flowing, it was a good(ish) refresher for incident response (can’t beat the adrenaline rush of responding to an incident, real or imagined) and rkhunter uncovered a potential weakness in the server configuration which has since been corrected (no, I’m not telling you what).
Running through my morning routine of catching up with email, twitter, etc. I came across this post showing Sequal7′s first hits on a Kippo installation. In addition to making amusing reading, it gave me a nudge to check back on the InfoSanity Kippo sensor. Initially I was looking to see if the same individual had stumbled across my sensor; they hadn’t at least not from the information I have available.
However, when checking if the newly changed password matched anything in my database I found a new ‘realm’ entry in the ‘input’ table, ‘ssh’. This got me curious, one of my ‘guests’ decided to hit another system whilst logged in to mine; ssh’ing to another IP, accepting the certificate and providing the password to said system (I’m assuming).
It should also be worth noting that by this point the user had already failed to notice that input hadn’t returned to their own system. After (attempting) to change my sensor’s root password (to ‘yahoo’, really) the user exited, but was caught out by Kippo’s trick of clearing the terminal and changing prompt to ‘localhost’, in total I viewed a ~20 minute terminal session of the user trying to compromise other systems, and failing in the same manner.
My assumption is that the user was running through a list of vulnerable systems identified by SSH scanners similar to the kit I wrote about earlier (it wasn’t the same gosh.tgz kit, but first glance shows similar functionality). From this I feel it’s safe to assume that the systems connected to in the logs available are those of other (probably 0wned) systems, rather than anything connected to my guest. Likewise it is probable that the source connection is also a compromised third party rather than belonging to by guest.
For the curious, archive contents:
Whilst investigating the individual exploits and files; I came across this post, indicating ‘my’ archive is a known fire and forget post exploit kit. Here be Skiddies…