A TCP header with the SYN and FIN flags set is anomalous TCP behavior, causing various responses from the recipient, depending on the OS. Blocking packets with SYN and FIN flags helps prevent OS system probes.
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Before You Begin |
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For background information, read Understanding Operating System Probes. |
To block packets with both the SYN and FIN flags set, use the JUNOS CLI configuration editor.
- user@host# set security screen syn-fin tcp syn-fin
- user@host# set security zones security-zone zone screen
syn-fin