105 lines
6.7 KiB
HTML
105 lines
6.7 KiB
HTML
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<meta name="DC.Title" content="Attack events" />
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<meta name="abstract" content="The intrusion detection system detects different types of attack events and writes an IM audit record in the QAUDJRN audit journal." />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Attack events</title>
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</head>
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<body id="rzaubeventattack"><a name="rzaubeventattack"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Attack events</h1>
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<div><p><span>The intrusion detection system detects different
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types of attack events and writes an IM audit record in the QAUDJRN audit
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journal.</span></p>
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<div class="section"><div class="p">The intrusion detection system detects the following
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types of attack events:<ul><li>Malformed packets</li>
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<li>Denial of service floods</li>
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<li>ICMP redirect messages</li>
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<li>Perpetual echo on UDP ports</li>
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<li>IP fragments</li>
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<li>Restricted IP options and protocols</li>
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<li>Fragmented packets</li>
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</ul>
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</div>
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<p>The number of audit records that the system generates
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depends on the value of the maximum event message in the IDS policy.</p>
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</div>
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<div class="section" id="rzaubeventattack__malformed"><a name="rzaubeventattack__malformed"><!-- --></a><h4 class="sectiontitle">Malformed packet events</h4><p>A malformed
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packet is built in such a way as to cause a system to crash or hang when it
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is processed. <span>When the IDS policy detects a malformed packet,
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it writes an audit record. The TCP/IP stack deletes the malformed packets.</span></p>
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</div>
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<div class="section" id="rzaubeventattack__fragment"><a name="rzaubeventattack__fragment"><!-- --></a><h4 class="sectiontitle">Fragment restriction events</h4><p>An
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invalid fragment overlays IP or transport headers in an attempt to bypass
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firewall checks. On the iSeries™ system, it is not possible to overlay an
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IP header. The TCP/IP stack checks to ensure that the first fragment of a
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fragmented datagram is a minimum of 576 bytes. The stack also checks that
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each fragment beyond the first one has an offset of greater than 256 bytes. </p>
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<p>The IDS policy audits invalid IP fragments.</p>
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</div>
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<div class="section" id="rzaubeventattack__ipoptionrestrict"><a name="rzaubeventattack__ipoptionrestrict"><!-- --></a><h4 class="sectiontitle">IP option restrictions</h4><p>The
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IP options field in a datagram is a variable-length list of optional information.
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Some of the IP Options, such as Loose Source Route, can be used in network
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attacks. You can use the IDS policy to restrict which IP options that an inbound
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packet can contain. For example, you can specify whether an inbound packet
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with a restricted IP option <span>be ignored or audited</span>.
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You also can generate statistics on the number of inbound packets with restricted
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IP options. </p>
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</div>
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<div class="section" id="rzaubeventattack__ipprotocol"><a name="rzaubeventattack__ipprotocol"><!-- --></a><h4 class="sectiontitle">IP protocol restrictions</h4><p>The IP
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protocol field is an 8-bit field in the IP header. Undefined IP protocols
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are sometimes used to establish back door attacks on the network. You can
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use the IDS policy to restrict which IP protocols that an inbound packet can
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contain. The policy can specify whether an inbound packet with a restricted
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IP protocol be audited. You also can generate statistics on the number of
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inbound packets with restricted IP protocols.</p>
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</div>
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<div class="section" id="rzaubeventattack__synflood"><a name="rzaubeventattack__synflood"><!-- --></a><h4 class="sectiontitle">SYN flood events</h4><p>TCP SYN flood events
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create a large number of half-open sockets. These flood events fill up the
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socket connection backlog for a given application and deny valid connections
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from being accepted. A SYN flood event spoofs the source IP address with the
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address of an unreachable system. The IDS policy flags SYN flood events and
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writes an audit record.</p>
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</div>
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<div class="section" id="rzaubeventattack__icmp"><a name="rzaubeventattack__icmp"><!-- --></a><h4 class="sectiontitle">ICMP redirect events</h4><p>You
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can use Internet Control Message Protocol (ICMP) redirect messages to override
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intended network routes. You can specify the IGNOREREDIRECT option in the
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IDS policy file to either ignore or process ICMP redirect messages.</p>
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</div>
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<div class="section" id="rzaubeventattack__echo"><a name="rzaubeventattack__echo"><!-- --></a><h4 class="sectiontitle">Perpetual echo on UDP ports</h4><p>You
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can use port 7, which is called the <dfn class="term">echo port</dfn>, to test a UDP
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connection. (Both the source port and target port are set to port 7, which
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causes each port to echo back what it gets.) Whatever data is sent through
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UDP is echoed back. A perpetual echo is an attack on UDP port 7. The TCP/IP
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stack detects the event if the source port is equal to the target port. If
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there is an IDS policy for attack-type events, the system writes an audit
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record whenever it detects a perpetual echo attack on the UDP port. </p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaubanalyze.htm" title="Learn how to analyze the auditing data for intrusion detection activities, and obtain reference information about the fields in the IM audit record.">Analyze the auditing data</a></div>
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</div>
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</div>
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</body>
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