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Title: BlackICE Agent Temporary Memory Buildup

BUG-ID: 2002023
Released: 17th Jun 2002
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!NOTE!
======
The vendor has asked us to include their reply in this bulletin. To
avoid too much duplicate information, we have decided to split the
vendors response into the relevant sections of this advisory. All
vendor quotes will be contained in quotes (").

Problem:
========
"The default settings for BlackICE Agent allow for an overly large
 number of TCP connections. A large number of open TCP connections
 coupled with a limited amount of memory can result in a limited
 Denial of Service (DoS) attack. Remote attackers on the same
 high-speed network segment may be able to launch an attack against
 a vulnerable BlackICE Agent. BlackICE Agents with an ample amount
 of memory outside a lab environment cannot be reliably attacked by
 exploiting this flaw."

It is possible for a malicious user to consume up to 400Mb of memory
on a host running BlackICE Agent. This attack can be performed over
the Internet.

Vulnerable:
===========
- BlackICE Agent 3.1 eal on Windows 2000 laptop
- BlackICE Agent 3.1 ebh on Windows 2000 laptop

Details:
========
"The BlackICE line includes multiple products which share a common
 code-base and require different tuning parameters. All products
 contain a Network Intrusion Detection System (NIDS) component. The
 desktop/server BlackICE Agent uses NIDS to monitor inbound and
 outbound traffic from a single desktop or server computer. The
 BlackICE Sentry monitors a specific network or segment, which
 contains traffic belonging to other devices.

 Since BlackICE Sentry monitors all traffic on the network segment,
 it must support monitoring multiple devices with many connections
 apiece. A single desktop typically has fewer than 10 TCP
 connections while a single server may have several hundred TCP
 connections. BlackICE Sentry may be monitoring hundreds of
 thousands of TCP connections at any time, and each TCP connection
 that is tracked requires memory.

 The desktop Agent version of BlackICE should be tuned to a maximum
 of 5,000 connections. The server Agent should be tuned to limit
 10,000 simultaneous connections. The Sentry version is tuned to
 handle 250,000 simultaneous TCP connections.

 This tuning eliminates the problem where the Agent is configured
 like Sentry, and continues to allocate memory until it reaches the
 limit of 250,000 simultaneous TCP connections."

When sending specially crafted TCP packets to ports on the
firewalled host, it starts allocating memory. Depending on the state
of the port that is attacked, it is possible to consume between 200
and 400MB of memory with this attack. The firewalled host will
recover on its own, which should take it 10-15 minutes.

Vendor URL:
===========
You can visit the vendor webpage here: http://www.iss.net

Vendor Response:
================
This was reported to the vendor on the 15th of March, 2002. On the
29th of May, 2002 the vendor reproduced the issue. On the 17th of
June, 2002 we received the vendors official response to the issue.

Corrective action:
==================
"ISS X-Force recommends that BlackICE Agent users reconfigure the
 maximum number of TCP connections to 5000 simultaneous connections.
 This setting can be adjusted by editing the local "blackice.ini"
 file, or by modifying this parameter via the ICEcap Management
 console:

 tcp.maxconnections=5000

 ISS will update the next version of BlackICE Agent with the correct
 tuning parameters."

Authors:
Andreas Sandor (asandorkpmg.dk)
Peter Gründl (pgrundlkpmg.dk)

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