Fortinet Protocol decoders, IPS sensors, DoS sensors, SYN flood attacks, Icmp sweep attacks

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Creating custom signatures	23
Custom signature fields	23
Custom signature syntax	24
Example custom signatures	33
Protocol decoders	37
Protocol decoders	37
Upgrading the IPS protocol decoder list	37
Viewing the protocol decoder list	38
IPS sensors	39
Viewing the IPS sensor list	39
Adding an IPS sensor	40
Configuring IPS sensors	40
Configuring filters	42
Configuring pre-defined and custom overrides	43
DoS sensors	45
Viewing the DoS sensor list	46
Configuring DoS sensors	46
Understanding the anomalies	48
SYN flood attacks	51
What is a SYN flood attack?	51
How SYN floods work	51
The FortiGate IPS Response to SYN flood attacks	52
What is SYN threshold?	52
What is SYN proxy?	52
How IPS works to prevent SYN floods	52
Configuring SYN flood protection	54
Suggested settings for different network conditions	54
ICMP sweep attacks	55
What is an ICMP sweep?	55
How ICMP sweep attacks work	55
The FortiGate IPS response to ICMP sweep attacks	55
Predefined ICMP signatures	56
ICMP sweep anomalies	57
Configuring ICMP sweep protection	58
Suggested settings for different network conditions	58
Index	59

	FortiGate IPS User Guide Version 3.0 MR7
4	01-30007-0080-20080916

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Contents E R G U I D E Trademarks Contents Protocol decoders IPS sensorsDoS sensors SYN flood attacksIntroduction FortiGate IPSAbout this document Fortinet documentationDocument conventions Typographic conventionsFortiGate Pptp VPN User Guide Fortinet Knowledge Center Customer service and technical supportComments on Fortinet technical documentation IPS settings and controls IPS overview and general configurationThis section contains the following topics When to use IPS Default signature and anomaly settingsDefault fail open setting Config ips global Set fail-open enable disable endSetting the buffer size Configuring logging and alert emailMonitoring the network and dealing with attacks Controlling sessionsAttack log messages Signature Anomaly FortiGuard CenterUsing IPS sensors in a protection profile Creating a protection profile that uses IPS sensorsAdding protection profiles to firewall policies Select Create NewAdding protection profiles to user groups Using IPS sensors in a protection profile IPS predefined signatures Predefined signaturesViewing the predefined signature list Settings EnableColumn Clear All FiltersCreate a sensor and add IPS filters to it Viewing the predefined signature list IPS custom signatures Custom signaturesViewing the custom signature list Custom signature configuration Adding custom signatures using the web-based managerAdding custom signatures using the CLI Command syntax patternCustom signature fields Creating custom signaturesShows the valid characters for custom signature fields Custom signature syntax AttackidName BufferOverflow SrcportContent keywords Keyword and value Description Deprecated, see pattern and context keywords Pattern GET Context uriPattern yahoo.com Context hostPcre Regex/mdelimRegexdelimismxAEGRU Uri !uristrProtocol tcp IP header keywords Keyword and Value DescriptionTCP header keywords Keyword and Value Description Tcpflags AP Tcpflags S,12Icmp keywords Keyword and Value Usage UDP header keywords Keyword and Value DescriptionOther keywords Keyword and Value Description Example custom signatures Example 1 signature to block access to example.comSbid --name Block.example.com Sbid --name Block.example.com Sbid --name Block.SMTP.VRFY.CMD Example 2 signature to block the Smtp ‘vrfy’ commandSbid --name Block.SMTP.VRFY.CMD --pattern vrfy Creating custom signatures Protocol decoders Protocol decodersUpgrading the IPS protocol decoder list Viewing the protocol decoder list Protocol decoder list Protocols Protocol decoder names PortAlldefault AlldefaultpassIPS sensors Viewing the IPS sensor listConfiguring IPS sensors Adding an IPS sensorProtectclient ProtectemailserverIPS sensor attributes IPS sensor filtersConfiguring filters ResetIPS sensor overrides Delete and Edit Delete or edit the filter IconsConfiguring pre-defined and custom overrides ApplicationExempt IP SourceDoS sensors Configuring DoS sensors Viewing the DoS sensor listSequence in which the sensors examine network traffic Appears, and select OKAnomaly configuration DoS sensor attributesName Enter or change the DoS sensor name Comments Will appear in the DoS sensor listUnderstanding the anomalies Anomaly Description Tcpdstsession UdpfloodUdpscan UdpsrcsessionUnderstanding the anomalies SYN flood attacks What is a SYN flood attack?How SYN floods work What is SYN threshold? What is SYN proxy?FortiGate IPS Response to SYN flood attacks How IPS works to prevent SYN floodsIPS operation before synflood threshold is reached Suggested settings for different network conditions Configuring SYN flood protectionConfigure the options for tcpsynflood Select OK What is an Icmp sweep? Icmp sweep attacksHow Icmp sweep attacks work FortiGate IPS response to Icmp sweep attacksPredefined Icmp signatures Icmp sweep anomalies Configuring Icmp sweep protection Index FortiGate Version 3.0 MR7 IPS User GuideTechnical support