Last revised: September 17, 1997
Attached copyright statement
A complete revision history is at the end of this file.
This is a repost of the Ultrix 3.0 advisory. We have received the sum output for DECstations.
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.
- Check for a bogus /usr/bin/login.
The sum program should report
the following for the DEC supplied login program.
27379 67 for VAXstation Ultrix 3.0 35559 116 for DECstation Ultrix 3.0
- Check for a bogus /usr/etc/telnetd. The sum program should report
the following for the DEC supplied telnetd program.
23552 47 for VAXstation Ultrix 3.0 45355 84 for DECstation Ultrix 3.0
- 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.
- Upgrade to Ultrix 3.1 ASAP.
- 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.
- Search through the file system for programs that are setuid root.
- 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.
Computer Emergency Response Team (CERT)
Copyright 1989 Carnegie Mellon University.
September 17,1997 Attached copyright statement