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CERT Advisory #8
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CERT Advisory
October 17, 1989
DEC/Ultrix 3.0 Systems
Recently, the CERT/CC has been working with several Unix sites that have
experienced breakins. Running tftpd, accounts with guessable passwords
or no passwords, and known security holes not being patched have been the
bulk of the problems.
The intruder, once in, gains root access and replaces key programs
with ones that create log files which contain accounts and passwords in
clear text. The intruder then returns and collects the file. By using
accounts which are trusted on other systems the intruder then installs
replacement programs which start logging.
There have been many postings about the problem from several other net
users. In addition to looking for setuid root programs in users' home
directories, hidden directories '.. ' (dot dot space space), and a modified
telnet program, we have received two reports from Ultrix 3.0 sites that
the intruders are replacing the /usr/bin/login program. The Ultrix security
hole being used in these attacks is only found in Ultrix 3.0.
Suggested steps:
1) Check for a bogus /usr/bin/login. The sum program reports:
27379 67 for VAX/Ultrix 3.0
2) Check for a bogus /usr/etc/telnetd. The sum program reports:
23552 47 for VAX/Ultrix 3.0
3) Look for .savacct in either /usr/etc or in users' directories.
This may be the file that the new login program creates. It
could have a different name on your system.
4) Upgrade to Ultrix 3.1 ASAP.
5) Monitor accounts for users having passwords that can be found in
the /usr/dict/words file or have simple passwords like a persons
name or their account name.
6) Search through the file system for programs that are setuid root.
7) Disable or modify the tftpd program so that anonymous access to
the file system is prevented.
If you find that a system that has been broken into, changing the password
on the compromised account is not sufficient. The intruders do remove copies
of the /etc/passwd file in order to break the remaining passwords. It is best
to change all of the passwords at one time. This will prevent the intruders
from using another account.
Please alert CERT if you do find a problem.
Thank you,
Ed DeHart
Computer Emergency Response Team
Email: [email protected]
Telephone: 412-268-7090 (answers 24 hours a day)
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