DNS: Z Option Set

This signature detects DNS requests that have the Z (reserved) option set. No RFC currently has a use defined for this option, therefore, its use is anomalous. Many Trojan BotNets use a pseudo-DNS format for command and control, which can trigger this signature.

Short Name
DNS:AUDIT:Z-RESERVED-OPT
Severity
Major
Recommended
False
Recommended Action
Drop
Category
DNS
Keywords
Option Set Z
Release Date
05/10/2012
Supported Platforms

srx-branch-12.3

srx-19.3

srx-branch-19.3

vsrx3bsd-19.2

srx-branch-19.4

vsrx-19.4

mx-12.3

mx-19.4

vmx-19.4

mx-19.3

vsrx3bsd-19.4

srx-19.4

vsrx-12.3

vmx-19.3

vsrx-19.2

srx-12.3

Sigpack Version
3324
Port
UDP/53
False Positive
Unknown

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