Enterprise QoS Solution Reference Network Design Guide

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Branch Router LAN Edge QoS Design 4-14 show policy show policy interface show ip access-list show ip nbar port-map Verification Command: show ip nbar port-map Enterprise QoS Solution Reference Network Design Guide Chapter 4 Branch Router QoS Design When NBAR custom PDLMs are used to identify applications, it is useful to verify that the ports bound to the PDLM have been entered correctly. This information is obtained with the show ip nbar port-map command. In this (filtered) example, Example 4-7, the TCP ports given for SAP (3200 through 3203 and 3600) were bound correctly to the Custom-01 NBAR PDLM. Example 4-7 show ip nbar port-map Verification Custom-PDLM TCP/UDP Port-Mapping Example BRANCH#60-C3745#show ip nbar port-map | include custom-01 port-map custom-01 tcp 3200 3201 3202 3203 3600 BRANCH#60-C3745# NBAR Known-Worm Classification and Policing Worms are nothing new. They’ve been around almost as long as the Internet itself (one of the first Internet worms was the Morris worm, released in November 1988). Typically, worms are self-contained programs that attack a system and try to exploit a vulnerability in the target. Upon successfully exploiting the vulnerability, the worm copies its program from the attacking host to the newly exploited system to begin the cycle again. Note A virus, which is slightly different from a worm, requires a vector to carry the virus code from one system to another. The vector can be either a word-processing document, an e-mail, or an executable program. The main element that distinguishes a worm from a virus is that a computer virus requires human intervention to facilitate its spreading, whereas worms (once released) propagate without requiring additional human intervention. Worms are comprised of three primary components (as illustrated in Figure 4-4): The enabling exploit code—The enabling exploit code is used to exploit a vulnerability on a system. Exploitation of this vulnerability provides access to the system and the capability to execute commands on the target system. A propagation mechanism—When access has been obtained through the enabling exploit, the propagation mechanism is used to replicate the worm to the new target. The method used to replicate the worm can be achieved through the use of the Trivial File Transfer Protocol (TFTP), FTP, or another communication method. When the worm code is brought to the new host, the cycle of infection can be started again. A payload—Some worms also contain payloads, which might include additional code to further exploit the host, modify data on the host, or change a web page. A payload is not a required component, and, in many cases, the worm’s enabling exploit code itself can be considered the payload. Version 3.3
Chapter 4 Branch Router QoS Design NBAR Versus Code Red Version 3.3 Figure 4-4 Anatomy of an Internet Worm Branch Router LAN Edge QoS Design Some worms use unique TCP/UDP ports to propagate. These types of worms are fairly simple to block using access lists (when the ports are known). Such ACLs can be configured on the branch switch (whenever supported) or on the branch router’s LAN edge. Other worms hijack legitimate TCP/UDP ports to carry their harmful payloads. For these latter types of worms, NBAR can be used at the branch LAN edge to perform deep-packet analysis and drop any packets that are carrying the payloads of known worms. Some of these known worms include Code Red, NIMDA, SQL Slammer, RPC DCOM/W32/MS Blaster, and Sasser. The following sections discuss how NBAR can be used for each of these types of worms. First released in July 2001, Code Red targeted Microsoft Internet Information Server (IIS) using a vulnerability in the IIS Indexing Service. Although the first variant of this worm did little damage because of a flaw in the random number–generator code used to generate addresses of hosts to exploit, a second variant appeared with the flaw fixed. This worm, CodeRedv2, spread quickly and became the most widespread and damaging worm to hit the Internet since the Morris worm. CodeRedv2’s success as a worm relied on the fact that the worm exploited the vulnerability in the IIS Indexing Service only as a means of gaining access to the host. This, coupled with the wide deployment of IIS as well as the large number of unpatched IIS web servers, contributed to the quick and wide-ranging spread of the worm. An estimated 360,000 hosts were infected within a period of 14 hours. CodeRedv2 temporarily replaced the home page of the web servers that it struck with a new page. Additionally, the code of the worm indicated that it was programmed to begin a packet-flooding DoS attack against a hard-coded IP address. (At the time, this was the IP address of the White House web server at http://www.whitehouse.gov.) The original Code Red payload is shown in Example 4-8. The initial infection attempt sends a large HTTP GET request to the target IIS server. Example 4-8 Original Code Red Payload 1—The Enabling Exploit Code 2—Propagation Mechanism 3—Payload 2001-08-04 16:32:23 24.101.17.216 - 10.1.1.75 80 GET /default.ida NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN NNNNNNNNNNNNNNNNNNNNNNNNNNN%u9090%u6858%ucbd3%u7801%u9090%u6858%ucbd Enterprise QoS Solution Reference Network Design Guide 4-15
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Enterprise QoS Solution Reference Network Design Guide

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