Rule:

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Sid:
408

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Summary:
This event is generated when a network host generates an ICMP Timestamp Reply in response to an ICMP Timestamp Request message.

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Impact:
Information-gathering.  An ICMP Timestamp Reply message is sent in response to an ICMP RTimestamp Request message.  If the ICMP Timestamp Reply message reaches the requesting host it indicates that the replying host is alive.

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Detailed Information:
ICMP Type 0 Code 0 is the RFC defined messaging type for ICMP Timestamp Reply datagrams.  This type of message is used to determine if a host is active on the network.

If ICMP type 8 (echo) traffic is filtered at a firewall, an attacker may try to use type 14 (timestamp) as an alternative.

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Attack Scenarios:
A remote attacker may use ICMP Timestamp Request datagrams to determine active hosts on the network in prelude of further attacks.

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Ease of Attack:
Numerous tools and scripts can generate this type of ICMP datagram.

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False Positives:
None known

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False Negatives:
None known
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Corrective Action:
Use ingress filtering to prevent ICMP Type 0 Code 8 messages from entering the network.

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Contributors:
Original rule writer unknown
Sourcefire Research Team
Matthew Watchinski (matt.watchinski@sourcefire.com)
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:
None


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