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Rule:

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Sid:
469

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Summary:
This event is generated when an ICMP ping typically generated by nmap is detected.

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Impact:
This could indicate a full scan by nmap which is sometimes indicative of
potentially malicious behavior.

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Detailed Information:
Nmap's ICMP ping, by default, sends zero data as part of the ping.
Nmap typically pings the host via icmp if the user has root
privileges, and uses a tcp-ping otherwise.  

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Attack Scenarios:
As part of an information gathering attempt, an attacker may use nmap
to see what hosts are alive on a given network.  If nmap is used for
portscanning as root, the icmp ping will occur by default unless the
user specifies otherwise (via '-P0').

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Ease of Attack:
Trivial.  Nmap requires little or no skill to operate.

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False Positives:
Possible.  The only current identifying feature of nmap's ICMP ping is
that the data size is 0.  It is entirely possible that other tools may
send icmp pings with zero data.

Kontiki delivery manager used on windows platforms to download
multimedia files is known to produce ICMP pings that can cause this
rule to generate many events.

avast! antivirus update feature is reported to produce ICMP pings with
zero data when connecting to the avast servers. This can occur every 40
seconds if no reply is received by the client.

The avast! client attempts to ping one of the following servers:

URL: http://www.asw.cz/iavs4pro
IP: 195.70.130.34

URL: http://www.avast.com/iavs4pro
IP: 66.98.166.72

URL: http://www.iavs.net/iavs4pro
IP: 207.44.156.15

URL: http://www.iavs.cz/iavs4pro
IP: 62.168.45.69

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False Negatives:
None currently.

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Corrective Action:
If you detect other suspicous traffic from this host (i.e., a
portscan), follow standard procedure to assess what threat this may
pose.  If you only detect the icmp ping, this may have simply been a
'ping sweep' and may be ignored.

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Contributors:
warchild@spoofed.org
Sourcefire Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:
www.insecure.org


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