Fortinet manual Custom signatures, IPS custom signatures, Viewing the custom signature list

Page 21


Custom signatures	IPS custom signatures

Custom signatures

Custom signatures provide the power and flexibility to customize the FortiGate Intrusion Protection system for diverse network environments. The FortiGate predefined signatures represent common attacks. If you use an unusual or specialized application or an uncommon platform, you can add custom signatures based on the security alerts released by the application and platform vendors.

You can also create custom signatures to help you block P2P protocols.

After creation, you need to specify custom signatures in IPS sensors created to scan traffic.

This section describes:

•IPS custom signatures

•Viewing the custom signature list

•Custom signature configuration

•Creating custom signatures

IPS custom signatures

The FortiGate predefined signatures cover common attacks. If an unusual or specialized application or an uncommon platform is being used, add custom signatures based on the security alerts released by the application and platform vendors.

Use custom signatures to block or allow specific traffic. For example, to block the SMTP “vrfy” command, add custom signatures similar to the following:

F-SBID( --name "Block.SMTP.VRFY.CMD"; --protocol tcp; --service SMTP; --pattern "vrfy"; --no_case; --context header; )

Note: If virtual domains are enabled on the FortiGate unit, IPS is configured separately in each VDOM. Sensors, filters, and custom signatures will only appear in the VDOM in which they were created.

Viewing the custom signature list

To view the custom signature list, go to Intrusion Protection > Signature >

Custom.

Figure 4: The custom signature list

FortiGate IPS User Guide Version 3.0 MR7
01-30007-0080-20080916	21

Image 21

Contents E R G U I D E Trademarks Contents IPS sensors Protocol decodersDoS sensors SYN flood attacksFortiGate IPS IntroductionFortinet documentation About this documentDocument conventions Typographic conventionsFortiGate Pptp VPN User Guide Customer service and technical support Fortinet Knowledge CenterComments on Fortinet technical documentation IPS overview and general configuration IPS settings and controlsThis section contains the following topics Default signature and anomaly settings When to use IPSDefault fail open setting Config ips global Set fail-open enable disable endConfiguring logging and alert email Setting the buffer sizeMonitoring the network and dealing with attacks Controlling sessionsAttack log messages Signature FortiGuard Center AnomalyCreating a protection profile that uses IPS sensors Using IPS sensors in a protection profileAdding protection profiles to firewall policies Select Create NewAdding protection profiles to user groups Using IPS sensors in a protection profile Predefined signatures IPS predefined signaturesViewing the predefined signature list Enable SettingsColumn Clear All FiltersCreate a sensor and add IPS filters to it Viewing the predefined signature list Custom signatures IPS custom signaturesViewing the custom signature list Adding custom signatures using the web-based manager Custom signature configurationAdding custom signatures using the CLI Command syntax patternCreating custom signatures Custom signature fieldsShows the valid characters for custom signature fields Attackid Custom signature syntaxName BufferOverflow SrcportContent keywords Keyword and value Description Deprecated, see pattern and context keywords Context uri Pattern GETPattern yahoo.com Context hostRegex/mdelim PcreRegexdelimismxAEGRU Uri !uristrIP header keywords Keyword and Value Description Protocol tcpTCP header keywords Keyword and Value Description Tcpflags S,12 Tcpflags APUDP header keywords Keyword and Value Description Icmp keywords Keyword and Value UsageOther keywords Keyword and Value Description Example 1 signature to block access to example.com Example custom signaturesSbid --name Block.example.com Sbid --name Block.example.com Example 2 signature to block the Smtp ‘vrfy’ command Sbid --name Block.SMTP.VRFY.CMDSbid --name Block.SMTP.VRFY.CMD --pattern vrfy Creating custom signatures Protocol decoders Protocol decodersUpgrading the IPS protocol decoder list Protocol decoder list Protocols Protocol decoder names Port Viewing the protocol decoder listAlldefaultpass AlldefaultIPS sensors Viewing the IPS sensor listAdding an IPS sensor Configuring IPS sensorsProtectclient ProtectemailserverIPS sensor filters IPS sensor attributesReset Configuring filtersIPS sensor overrides Delete and Edit Delete or edit the filter IconsApplication Configuring pre-defined and custom overridesSource Exempt IPDoS sensors Viewing the DoS sensor list Configuring DoS sensorsSequence in which the sensors examine network traffic Appears, and select OKDoS sensor attributes Anomaly configurationName Enter or change the DoS sensor name Comments Will appear in the DoS sensor listUnderstanding the anomalies Udpflood Anomaly Description TcpdstsessionUdpscan UdpsrcsessionUnderstanding the anomalies What is a SYN flood attack? SYN flood attacksHow SYN floods work What is SYN proxy? What is SYN threshold?FortiGate IPS Response to SYN flood attacks How IPS works to prevent SYN floodsIPS operation before synflood threshold is reached Configuring SYN flood protection Suggested settings for different network conditionsConfigure the options for tcpsynflood Select OK Icmp sweep attacks What is an Icmp sweep?How Icmp sweep attacks work FortiGate IPS response to Icmp sweep attacksPredefined Icmp signatures Icmp sweep anomalies Configuring Icmp sweep protection FortiGate Version 3.0 MR7 IPS User Guide IndexTechnical support