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Jnxjsscreenmontable jnxJsScreenMonTable The jnxJsScreenMonTable, whose object ID is {jjnxJsScreenObjects 1}, collects the screen attributes that monitor the various attacks to enable the Juniper Networks Security Firewall to provide deep inspection (DI) protection on each of the security device's physical interfaces. These attributes are listed in jnxJsLoadedCaCertTable. The screen options can be enabled at a security zone bounded to an interface or interfaces. When these options apply to traffic reaching the security device through interfaces (via a zone), they offer protection against a malicious information gathering probe or an attack to compromise, disable, or harm a network or network resources. Table 1: jnxJsScreenMonTable Object Object ID Description jnxJsScreenMonEntry jnxJsScreenMonTable The screen option monitoring statistics entry. Each entry is uniquely 1 identified by the zone name. The data is collected on a per zone basis. There can be multiple interfaces bound to a particular zone. Hence, the statistics are aggregated across the interfaces on a per zone basis. Sequence of parameters: ■ jnxJsScreenZoneName ■ jnxJsScreenNumOfIf ■ jnxJsScreenMonSynAttk ■ jnxJsScreenMonTearDrop ■ jnxJsScreenMonSrcRoute ■ jnxJsScreenMonPingDeath ■ jnxJsScreenMonAddrSpoof ■ jnxJsScreenMonLand ■ jnxJsScreenMonIcmpFlood ■ jnxJsScreenMonUdpFlood ■ jnxJsScreenMonWinnuke ■ jnxJsScreenMonPortScan ■ jnxJsScreenMonIpSweep ■ jnxJsScreenMonSynFrag ■ jnxJsScreenMonTcpNoFlag ■ jnxJsScreenMonIpUnknownProt ■ jnxJsScreenMonIpOptBad ■ jnxJsScreenMonIpOptRecRt—Record route option ■ jnxJsScreenMonIpOptTimestamp—Timestamp option ■ jnxJsScreenMonIpOptSecurity ■ jnxJsScreenMonIpOptLSR—Loose source route ■ jnxJsScreenMonIpOptSSR—Strict source route ■ jnxJsScreenMonIpOptStream—Stream options ■ jnxJsScreenMonIcmpFrag jnxJsScreenMonTable ■ 1 Table 1: jnxJsScreenMonTable (continued) Object Object ID Description ■ jnxJsScreenMonIcmpLarge ■ jnxJsScreenMonTcpSynFin ■ jnxJsScreenMonTcpFinNoAck ■ jnxJsScreenMonLimitSessSrc—Session limit (source IP-based) ■ jnxJsScreenMonLimitSessDest—Session limit (destination IP-based) ■ jnxJsScreenMonSynAckAck ■ jnxJsScreenMonIpFrag ■ jnxJsScreenSynAttackThresh—Threshold data ■ jnxJsScreenSynAttackThresh—Threshold data ■ jnxJsScreenSynAttackTimeout—Threshold data ■ jnxJsScreenSynAttackAlmTh—Threshold data ■ jnxJsScreenSynAttackQueSize—Threshold data ■ jnxJsScreenSynAttackAgeTime—Threshold data (obsolete in this release) ■ jnxJsScreenIcmpFloodThresh—Threshold data ■ jnxJsScreenUdpFloodThresh—Threshold data ■ jnxJsScreenPortScanThresh—Threshold data ■ jnxJsScreenIpSweepThresh—Threshold data ■ jnxJsScreenSynAckAckThres—Threshold data jnxJsScreenZoneName jnxJsScreenMonEntry Name of the security zone under which the statistics are collected. 1 jnxJsScreenNumOfIf jnxJsScreenMonEntry Number of interfaces bound to this zone. Each counter contains the 2 aggregated data of all the interfaces. jnxJsScreenMonSynAttk jnxJsScreenMonEntry Number of SYN (TCP connection request) attacks. 3 A SYN attack is a common denial of service (DoS) technique characterized by the following pattern: ■ Using a spoofed IP address not in use on the Internet, an attacker sends multiple SYN packets to the target machine. ■ For each SYN packet received, the target machine allocates resources and sends an acknowledgement (SYN-ACK) to the source IP address. This can cause the target machine to allocate resources for more than 3 minutes to respond to just one SYN attack, subsequently wasting resources. jnxJsScreenMonTearDrop jnxJsScreenMonEntry Number of teardrop attacks. 4 Teardrop attacks exploit the reassembly of fragmented IP packets. In the IP header, one of the fields is the fragment offset field, which indicates the starting position of the data contained in a fragmented packet relative to the data of the original unfragmented packet. When the sum of the offset and size of one fragmented packet differ from that of the next fragmented packet, the packets overlap. The server 2 ■ jnxJsScreenMonTable Table 1: jnxJsScreenMonTable (continued) Object Object ID Description attempting to reassemble the packet can crash, especially if it is running an older operating system that has this vulnerability. When this option is enabled, the security device detects this discrepancy in a fragmented packet and drops it, and counts the number of packet dropped. jnxJsScreenMonSrcRoute jnxJsScreenMonEntry Number of either loose source route option packets or strict source 5 route attack packets. IP source route options can be used to hide their true address and access restricted areas of a network by specifying a different path. The security device should be able to either block any packets with loose or strict source route options set or detect such packets and then record the event for the ingress interface. jnxJsScreenMonPingDeath jnxJsScreenMonEntry Number of ping-of-death attack packets. 6 The maximum allowable IP packet size is 65,535 bytes, including the packet header (typically 20 bytes long). An ICMP echo request is an IP packet with a pseudo header, which is 8 bytes long. Therefore, the maximum allowable size of the data area of an ICMP echo request is 65,507 bytes. Many ping implementations, however, allow the user to specify a packet size larger than 65,507 bytes. A grossly oversized ICMP packet can trigger a range of adverse system reactions, such as DoS, crashing, freezing, and rebooting. When the ping-of-death option is enabled, the security device detects and rejects such oversized and irregular packet sizes, even when the attacker hides the total packet size by purposefully fragmenting it. jnxJsScreenMonAddrSpoof jnxJsScreenMonEntry Number of address spoofing attack packets. 7 One method to gain access to a restricted network is to insert a bogus source address in the packet header to make the packet appear to come from a trusted source. This technique is called IP spoofing. The mechanism to detect IP spoofing relies on route table entries. For example, if a packet with source IP address 10.1.1.6 arrives at port eth3, but the security device has a route to 10.1.1.0/24 through port eth1, IP spoofing checking notes that this address arrived at an invalid interface as defined in the route table. A valid packet from 10.1.1.6 can arrive only through eth1, not eth3. The security device concludes that the packet has a spoofed source IP address and discards it. jnxJsScreenMonLand jnxJsScreenMonEntry Number of land attack packets. 8 A SYN attack combined with an IP spoof is referred to as land attack. A land attack occurs when an attacker sends spoofed SYN packets containing the IP address of the victim as both the destination and source IP address. The receiving victim responds by sending the SYN-ACK packet to itself, creating an empty connection that lasts jnxJsScreenMonTable ■ 3 Table 1: jnxJsScreenMonTable (continued) Object Object ID Description until the idle timeout value is reached. Flooding a system with such empty connections can overwhelm the victim, causing a DoS. jnxJsScreenMonIcmpFlood jnxJsScreenMonEntry Number of ICMP flood attack packets. 9 An ICMP flood typically occurs when ICMP echo requests overload a victim with so many requests that the victim expends all its resources responding to the ICMP echo requests until it can no longer process valid network traffic. With ICMP flood protection enabled and a threshold set, if the threshold is exceeded, the victim invokes the flood attack protection feature. The default threshold value is 1000 pps. If the threshold is exceeded, the security device ignores further ICMP echo requests for the remainder of that second plus the next second as well. jnxJsScreenMonUdpFlood jnxJsScreenMonEntry Number of UDP flood attack packets. 10 UDP flooding occurs when an attacker sends IP packets containing UDP datagrams with the purpose of slowing down the victim to the point that it can no longer handle valid connections. With UDP flood protection enabled, a threshold can be set so that when the threshold is exceeded, the system invokes UDP flood attack protection. The default threshold value is 1000 pps. If the number of UDP datagrams from one or more sources to a single destination exceeds this threshold, the security device ignores further UDP datagrams to that destination for the remainder of that second plus the next second as well. jnxJsScreenMonWinnuke jnxJsScreenMonEntry Number of NetBIOS attacks. 11 WinNuke is a DoS attack targeting any computer on the Internet running Microsoft Windows. The attacker sends a TCP segment, usually to NetBIOS port 139 of a host with an established connection with segment's urgent (URG) flag set. This practice introduces a NetBIOS fragment overlap, which causes many machines running Microsoft Windows to crash. jnxJsScreenMonPortScan jnxJsScreenMonEntry Number of port scan attempt attack packets. 12 A port scan occurs when one source IP address sends IP packets containing TCP SYN segments to a defined number of different ports at the same destination IP address within a defined interval. The purpose of this attack is to scan the available services in the hope that at least one port will respond, thus identifying a service of the target. The security device should internally log the number of different ports scanned from one remote source. jnxJsScreenMonIpSweep jnxJsScreenMonEntry Number of address sweep attempt attack packets. 13 An address sweep occurs when one source IP address sends a defined number of ICMP packets to different hosts within a defined interval. The purpose of this attack is to send ICMP
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