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Information about telnet sessions

Recently, I was asked this:

Is there a way to identify which telnet session corresponds to which ptty? I would like to know the remote ip address and the ptty of each telnet session

On Linux and BSD systems, "w" shows both where logins came from and what tty they use. For SCO Unix, you need to use "w -x".

If you need to distinguish ssh from telnet, see How can I tell if a user logged in locally, used rlogin, telnet or ssh?

For even more information, "lsof" can tell you what is really going on. You might start with "lsof -i:23", or if you already know the process id's, go directly to "lsof -p xyzx" (xyzx being a PID you want to examine).

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© Tony Lawrence

---December 21, 2004

lsof is one of the most useful commands when trying to figure out what is going on in any *nix system. I have only used it with SCO, and Linux, but I am sure that Solaris, HP-UX, AIX, and the others have similar uses for lsof.

Here are some of the links I have used to learn the usefulness of lsof in the past:



It can also be used for forensic analysis, should your system become comprimised. Of course, some Trojan Horses replace lsof with a trojaned one, that hides processes running by the trojan, so always be sure to install a fresh copy of lsof from a trusted source or backup, before you begin your forensic traces.



---December 21, 2004

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