Configuring TCP SYN Flood Attack Screen

date_range 29-Sep-23

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This topic describes how to configure detection of a TCP SYN flood attack.

A SYN flood occurs when a host is so overwhelmed by SYN segments initiating incomplete connection requests that it can no longer process legitimate connection requests.

To enable detection of a TCP SYN flood attack:

Configure interfaces and assign an IP address to interfaces.

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user@host# set interfaces ge-0/0/1 unit 0 family inet address 192.0.2.0/24
user@host# set interfaces ge-0/0/3 unit 0 family inet address 198.51.100.0/24

Configure security zones trustZone and untrustZone and assign interfaces to them.

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user@host# set security zones security-zone trustZone host-inbound-traffic system-services all
user@host# set security zones security-zone trustZone host-inbound-traffic protocols all
user@host# set security zones security-zone trustZone interfaces ge-0/0/1.0
user@host# set security zones security-zone untrustZone host-inbound-traffic system-services all
user@host# set security zones security-zone untrustZone host-inbound-traffic protocols all
user@host# set security zones security-zone untrustZone interfaces ge-0/0/3.0

Configure security policies from untrustZone to trustZone.

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user@host# set security policies from-zone untrustZone to-zone trustZone policy policy1 match source-address any
user@host# set security policies from-zone untrustZone to-zone trustZone policy policy1 match destination-address any
user@host# set security policies from-zone untrustZone to-zone trustZone policy policy1 match application any
user@host# set security policies from-zone untrustZone to-zone trustZone policy policy1 then permit
user@host# set security policies default-policy deny-all

Configure security screens and attach them to untrustZone.

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user@host# set security screen ids-option untrustScreen tcp syn-flood
user@host# set security screen ids-option untrustScreen alarm-without-drop
user@host# set security zones security-zone untrustZone screen untrustScreen

Configure syslog.

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user@host# set system syslog file syslog any any
user@host# set system syslog file syslog archive size 10000000
user@host# set system syslog file syslog explicit-priority
user@host# set system syslog file syslog structured-data
user@host# set security policies from-zone untrustZone to-zone trustZone policy policy1 then log session-init
user@host# set security policies from-zone untrustZone to-zone trustZone policy policy1 then log session-close

Commit the configuration.
```
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user@host# commit
```

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Configuring TCP SYN Flood Attack Screen

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