Security hole? undefined user appeared!

[Nan Xu]

Hi Everyone.

About 4days beofre I meet a very strange thing like the picture 1, there is a undefined user appeared.

I am very sure we have not a user "root".

Even we have a username "root"  we have a acl in the lien vty, this ip address is not in the permit list. how it can login in our device ?

I check the log server I notice there are some ssh log in the log server. (picture 3)

The ios version is picture 2.

I have a some question about this is my device hacked by somebady?  Is there any bug cause this ?  upgrade ios is useful?

Thanks for yours help

regards

[Joseph Fischer · Accepted solution]

What I would start with is locking down all vty lines. Change the password and make sure you are using the range command. It could have been you only secured line vty 0.

Then backup your settings and re-flash the rom if your concerned that it has been breached.

I'm not a expert but you can try these steps as your waiting for one. More details would also be helpful.

[Miroslav Berkov]

Have a look on Snowden papers, the NSA ordinary use root account to access on some Cisco routers