bostic@OKEEFFE.BERKELEY.EDU (Keith Bostic) (11/03/88)
Subject: Fixes for the virus
Index: usr.lib/sendmail/src/srvrsmtp.c 4BSD
Description:
There's a virus running around; the salient facts. A bug in
sendmail has been used to introduce a virus into a lot of
Internet UNIX systems. It has not been observed to damage the
host system, however, it's incredibly virulent, attempting to
introduce itself to every system it can find. It appears to
use rsh, broken passwords, and sendmail to introduce itself
into the target systems. It affects only VAXen and Suns, as
far as we know.
There are three changes that we believe will immunize your
system. They are attached.
Thanks to the Experimental Computing Facility, Center for
Disease Control for their assistance. (It's pretty late,
and they certainly deserved some thanks, somewhere!)
Fix:
First, either recompile or patch sendmail to disallow the `debug'
option. If you have source, recompile sendmail after first
applying the following patch to the module svrsmtp.c:
*** /tmp/d22039 Thu Nov 3 02:26:20 1988
--- srvrsmtp.c Thu Nov 3 01:21:04 1988
***************
*** 85,92 ****
"onex", CMDONEX,
# ifdef DEBUG
"showq", CMDDBGQSHOW,
- "debug", CMDDBGDEBUG,
# endif DEBUG
# ifdef WIZ
"kill", CMDDBGKILL,
# endif WIZ
--- 85,94 ----
"onex", CMDONEX,
# ifdef DEBUG
"showq", CMDDBGQSHOW,
# endif DEBUG
+ # ifdef notdef
+ "debug", CMDDBGDEBUG,
+ # endif notdef
# ifdef WIZ
"kill", CMDDBGKILL,
# endif WIZ
Then, reinstall sendmail, refreeze the configuration file,
using the command "/usr/lib/sendmail -bz", kill any running
sendmail's, using the ps(1) command and the kill(1) command,
and restart your sendmail. To find out how sendmail is
execed on your system, use grep(1) to find the sendmail start
line in either the files /etc/rc or /etc/rc.local
If you don't have source, apply the following patch to your
sendmail binary. SAVE A COPY OF IT FIRST, IN CASE YOU MESS
UP! This is mildly tricky -- note, some versions of strings(1),
which we're going to use to find the offset of the string
"debug" in the binary print out the offsets in octal, not
decimal. Run the following shell line to decide how your
version of strings(1) works:
/bin/echo 'abcd' | /usr/ucb/strings -o
Note, make sure the eight control 'G's are preserved in this
line. If this command results in something like:
0000008 abcd
your strings(1) command prints out locations in decimal, else
it's octal.
The patch script for sendmail. NOTE, YOUR OFFSETS MAY VARY!!
This script assumes that your strings(1) command prints out
the offsets in decimal.
Script started on Thu Nov 3 02:08:14 1988
okeeffe:tmp {2} strings -o -a /usr/lib/sendmail | egrep debug
0096972 debug
okeeffe:tmp {3} adb -w /usr/lib/sendmail
?m 0 0xffffffff 0
0t10$d
radix=10 base ten
96972?s
96972: debug
96972?w 0
96972: 25701 = 0
okeeffe:tmp {4} ^D
script done on Thu Nov 3 02:09:31 1988
If your strings(1) command prints out the offsets in octal,
change the line "0t10$d" to "0t8$d".
After you've fixed sendmail, move both /bin/cc and /bin/ld to
something else. (The virus uses the cc and the ld commands
to rebuild itself to run on your system.)
Finally, kill any processes on your system that don't belong there.
Suspicious ones have "(sh)" or "xNNNNNNN" where the N's are random
digits, as the command name on the ps(1) output line.
One more thing, if you find files in /tmp or /usr/tmp that
have names like "xNNNNNN,l1.c", or "xNNNNNN,sun3.o", or
"xNNNNNNN,vax.o" where the N's are random digits, you've been
infected.