CA-89:05 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 (CERT) Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 Internet: cert@cert.sei.cmu.edu Telephone: 412-268-7090 24-hour hotline: CERT personnel answer 7:30a.m.-6:00p.m. EST, on call for emergencies other hours. Past advisories and other information are available for anonymous ftp from cert.sei.cmu.edu (128.237.253.50).