Can you get a virus or any kind of malware by telneting?
You got a yes and a no answer because your question is kind of
ambiguous. There are various file transfer protocols that are used
with telnet (eg zmodem, kermit, ftp) and while files are being
transferred there is always the chance of getting some malware. So
although it's not specifically telnet which might cause the problem it
might happen while you are telnetting.
Another angle to look at is security. It isn't secure and usernames
and passwords etc. get sent in the open giving someone the opportunity
to nick your credentials and behave mischievously or fraudulently.
There are more secure alternatives (eg ssh) you can use which address
these security issues.
Jim.