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a-02.ciac-vms-worm-w_com

a-02.ciac-vms-worm-w_com
Posted Sep 23, 1999

a-02.ciac-vms-worm-w_com

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a-02.ciac-vms-worm-w_com

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_____________________________________________________________________________
T H E C O M P U T E R I N C I D E N T A D V I S O R Y C A P A B I L I T Y

C I A C

A D V I S O R Y N O T I C E
_____________________________________________________________________________

The W.COM Worm affecting VAX VMS Systems

October 16, 1989 18:37 PST Number A-2


Summary

A worm is attacking NASA's SPAN network via Vax/VMS systems connected
to DECnet. It is unclear if the spread of the worm has been checked.
It may spread to other systems such as DoE's HEPNET within a few days.
VMS system managers should prepare now. The worm targets VMS machines,
and can only be propagated via DECnet. The worm exploits two features
of DECnet/VMS in order to propagate itself. The first is the default
DECnet account, which is a facility for users who don't have a specific
login ID for a machine to have some degree of anonymous access. It uses
the default DECnet account to copy itself to a machine, and then uses
the "TASK 0" feature of DECnet to invoke the remote copy. It has
several other features including a brute force attack on passwords. An
analysis of the worm is provided below. Included with the analysis is
a DCL program that will block the current version of the worm. This
should give your system administrator enough time to close obvious
security holes. This worm exploits poor security practices, so you
must take action now to assure that the worm will not propagate to your
system(s).

If your site may be affected, please contact us for further
information. Information on how to contact CIAC appears at the end
of this notice.

________________________________________________________________________
This is a mean bug to kill and could have done a lot of damage.
Since it notifies (by mail) someone of each successful penetration
and leaves a trapdoor (the FIELD account), just killing the bug is
not adequate. You must go in an make sure all accounts have
passwords and that the passwords are not the same as the account
name.
R. Kevin Oberman
________________________________________________________________________


Advisory Notice

A worm is attacking NASA's SPAN network via
Vax/VMS systems connected to DECnet. It is unclear if the spread of the
worm has been checked. It may spread to other systems such as DOE's
HEPNET within a few days. VMS system managers should prepare now. The
worm targets VMS machines, and can only be propagated via DECnet. The
worm exploits two features of DECnet/VMS in order to propagate itself.
The first is the default DECnet account, which is a facility for users
who don't have a specific login ID for a machine to have some degree of
anonymous access. It uses the default DECnet account to copy itself to a
machine, and then uses the "TASK 0" feature of DECnet to invoke the
remote copy. It has several other features including a brute force
attack.

Once the worm has successfully penetrated your system it will infect
.COM files and create new security vulnerabilities. It then seems to
broadcast these vulnerabilities to the outside world. It may also
damage files as well, either unintentionally or otherwise.

An analysis of the worm appears below and is provided by R. Kevin Oberman of
Lawrence Livermore National Laboratory. Included with the analysis is a
DCL program that will block the current version of the worm. At least
two versions of this worm exist and more may be created. This program
should give you enough time to close up obvious security holes. A
more thorough DCL program is being written.

If your site could be affected please call CIAC for more details...

Report on the W.COM worm.
R. Kevin Oberman
Engineering Department
Lawrence Livermore National Laboratory
October 16, 1989

The following describes the action of the W.COM worm (currently based on the
examination of the first two incarnations). The replication technique causes
the code to be modified slightly which indicates the source of the attack and
learned information.

All analyis was done with more haste than I care for, but I believe I have all
of the basic facts correct.

First a description of the program:

1. The progam assures that it is working in a directory to which the owner
(itself) has full access (Read, Write,Execute, and Delete).

2. The program checks to see if another copy is still running. It looks for a
process with the first 5 characters of "NETW_". If such is found, it deletes
itself (the file) and stops its process.

NOTE
A quick check for infection is to look for a process name starting with
"NETW_". This may be done with a SHOW PROCESS command.

3. The program then changes the default DECNET account password to a random
string of at least 12 characters.

4. Information on the password used to access the system is mailed to the user
GEMTOP on SPAN node 6.59. Some versions may have a different address.

5. The process changes its name to "NETW_" followed by a random number.

6. It then checks to see if it has SYSNAM priv. If so, it defines the system
announcement message to be the banner in the program:
W O R M S A G A I N S T N U C L E A R K I L L E R S
_______________________________________________________________
\__ ____________ _____ ________ ____ ____ __ _____/
\ \ \ /\ / / / /\ \ | \ \ | | | | / / /
\ \ \ / \ / / / /__\ \ | |\ \ | | | |/ / /
\ \ \/ /\ \/ / / ______ \ | | \ \| | | |\ \ /
\_\ /__\ /____/ /______\ \____| |__\ | |____| |_\ \_/
\___________________________________________________/
\ /
\ Your System Has Been Officically WANKed /
\_____________________________________________/

You talk of times of peace for all, and then prepare for war.

7. If it has SYSPRV, it disables mail to the SYSTEM account.

8. If it has SYSPRV, it modifies the system login command procedure to
APPEAR to delete all of a user's file. (It really does nothing.)

9. The program then scans the account's logical name table for command
procedures and tries to modify the FIELD account to a known password
with login form any source and all privs. This is a primitive virus,
but very effective IF it should get into a privileged account.

10. It proceeds to attempt to access other systems by picking node numbers at
random. It then used PHONE to get a list of active users on the remote system.
It proceeds to irritate them by using PHONE to ring them.

11. The program then tries to access the RIGHTSLIST file and attempts
to access some remote system using the users found and a list of
"standard" users included withing the worm. It looks for passwords
which are the same as that of the account or are blank. It records all
such accounts.

12. It looks for an account that has access to SYSUAF.DAT.

13. If a priv. account is found, the program is copied to that account and
started. If no priv account was found, it is copied to other accounts found on
the random system.

14. As soon as it finishes with a system, it picks another random system and
repeats (forever).

Response:

1. The following program will block the worm. Extract the following code
and execute it. It will use minimal resources. It create a process named
NETW_BLOCK which will prevent the worm from running.
-------
Editors note: This fix will work only with this version of the worm.
Mutated worms will require modification of this code; however, this
program should prevent the worm from running long enough to secure
your system from the worms attacks.
-------
==============================================================================
$ Set Default SYS$MANAGER
$ Create BLOCK_WORM.COM
$ DECK/DOLLAR=END_BLOCK
$LOOP:
$ Set Process/Name=NETW_BLOCK
$ Wait 12:0
$ GoTo loop
END_BLOCK
$ Run/Input=SYS$MANAGER:BLOCK_WORM.COM/Error=NL:/Output=NL:/UIC=[1,4] -
SYS$SYSTEM:LOGINOUT
==============================================================================

2. Enable security auditing. The following command turns on the MINIMUM
alarms. The log is very useful in detecting the effects of the virus left by
the worm. It will catch the viruses modification of the UAF.
$ Set Audit/Alarm/Enable=(ACL,Authorization,Breakin=All,Logfailure=All)

3. Check for any account with NETWORK access available for blank passwords or
passwords that are the same as the username. Change them!

4. If you are running VMS V5.x, get a copy of SYS$UPDATE:NETCONFIG_UPDATE.COM
from any V5.2 system and run it. If you are running V4.x, change the username
and password for the network object "FAL".

5. If you have been infected, it will be VERY obvious. Start checking the
system for modifications to the FIELD account. Also, start scanning the system
for the virus. Any file modified will contain the following line:
$ oldsyso=f$trnlnm("SYS$OUTPUT")
It may be in LOTS of command procedures. Until all copies of the virus are
eleiminated, the FIELD account may be changed again.

6. Once you are sure all of the holes are plugged, you might kill off
NETW_BLOCK. (And then again, maybe not.)

Conclusion:

This is a mean bug to kill and could have done a lot of damage. Since it
notifies (by mail) someone of each successful penetration and leaves a trap
door (the FIELD account), just killing the bug is not adequate. You must go in
an make sure all accounts have passwords and that the passwords are not the
same as the account name.

R. Kevin Oberman
Lawrence Livermore National Laboratory
Internet: oberman@icdc.llnl.gov
(415) 422-6955


________________________________________________________________________
If you have any questions please contact either of the following CIAC team
members:

Dave Brown, (415) 423-9878 or FTS 543-9878
or
Gene Schultz, (415) 422-8193 or FTS 532-8193
or send electronic mail to:
ciac@tiger.llnl.gov


CIAC FAX: (415) 423-0913 FTS 543-0913

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