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FW: UNIRAS ALERT - 30/03 - Windows Messenger Vulnerability


- -----Original Message-----
From: UNIRAS (UK Govt CERT) [mailto:uniras@xxxxxxxxxxxx]
Sent: 20 October 2003 14:40
To: uniras@xxxxxxxxxxxx
Subject: UNIRAS ALERT - 30/03 - Windows Messenger Vulnerability


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   UNIRAS (UK Govt CERT) ALERT - 30/03 dated 20.10.03  Time: 14:41
 UNIRAS is part of NISCC(National Infrastructure Security Co-ordination Centre)
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  UNIRAS material is also available from its website at www.uniras.gov.uk and
         Information about NISCC is available from www.niscc.gov.uk
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Windows Messenger Vulnerability


Microsoft Bulletin MS03-043 describes a critical vulnerability in the Windows Messenger service that could allow an
attacker to create a Denial of Service condition or execute code on a remote system running Windows NT, Windows 2000,
Windows XP, or Windows Server 2003.  Uniras Brief 574/03 refers.

Proof of concept code has been published which reportedly causes a Windows 2000 computer to reboot.  There are also
reports that this PoC code is readily modifiable to return a shell on a remote Windows 2000 system.  Modification to run
on other Windows platforms should also be achievable with moderate effort.

Given that an attack can be delivered by UDP this vulnerability is prone to exploitation by a rapidly propagating worm
with source address obfuscation.


Uniras recommends that Departmental and Organisational Security Officers ensure that appropriate countermeasures are
implemented as soon as possible.

The Microsoft bulletin at http://www.microsoft.com/technet/security/bulletin/MS03-043.asp lists the location of patches
that address this issue.

In line with existing protective security advice the following ports should be blocked inbound and outbound at all
externally facing gateways:

     135 TCP/UDP
     137 UDP
     138 UDP
     139 TCP
     445 TCP/UDP
It should be noted that Windows Messenger is also found listening on ephemeral ports (i.e. above 1023).  The specific
port number is fairly predictable and so an attack directed at the most common (i.e. low-numbered) ephemeral ports can
also be expected.

If the Windows Messenger service is not required it should be disabled.  It is disabled by default only on Windows
Server 2003 platforms.
The management of systems moving from outside the perimeter to inside it, e.g. laptop computers used both at home and in
the office, should be reviewed to ensure that this common source of worm infection is adequately defended against.

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For additional information or assistance, please contact the HELP Desk by 
telephone or Not Protectively Marked information may be sent via EMail to:

Office Hours:
Mon - Fri: 08:30 - 17:00 Hrs
Tel: +44 (0) 20 7821 1330 Ext 4511
Fax: +44 (0) 20 7821 1686

Outside of Office Hours:
On Call Duty Officer:
Tel: +44 (0) 20 7821 1330 and follow the prompts

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This Briefing contains the information released by the original author. Some 
of the information may have changed since it was released. If the vulnerability 
affects you, it may be prudent to retrieve the advisory from the canonical site 
to ensure that you receive the most current information concerning that problem.

Reference to any specific commercial product, process, or service by trade 
name, trademark manufacturer, or otherwise, does not constitute or imply 
its endorsement, recommendation, or favouring by UNIRAS or NISCC.  The views 
and opinions of authors expressed within this notice shall not be used for 
advertising or product endorsement purposes.

Neither UNIRAS or NISCC shall also accept responsibility for any errors 
or omissions contained within this briefing notice. In particular, they shall 
not be liable for any loss or damage whatsoever, arising from or in connection 
with the usage of information contained within this notice.

UNIRAS is a member of the Forum of Incident Response and Security Teams (FIRST) 
and has contacts with other international Incident Response Teams (IRTs) in 
order to foster cooperation and coordination in incident prevention, to prompt 
rapid reaction to incidents, and to promote information sharing amongst its 
members and the community at large. 
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<End of UNIRAS Briefing>
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