GEN:SID 1:448
Message ICMP Source Quench undefined code
Summary This event is generated when an ICMP "Source Quench" message is
generated that has a non-zero ICMP code.  
Impact Informational.  This may indicate that the ICMP message has been
crafted.
Detailed Information An ICMP "Source Quench" message is issued by a network device that
cannot handle the current volume of traffic.  The ICMP code value for
this message should be 0.  If a non-zero ICMP code is observed, it may
be an indication that the packet was crafted with an invalid value.

ICMP Source Quench messages may be normally sent by either a gateway or
a host as a congestion control mechanism. A gateway would send them if
it is running out of buffer space (needed to queue datagrams for output
to the next hop) or by a host that is receiving datagrams too fast to
process. Maliciously crafted ICMP Source Quench Messages may be used to
force a remote host to slow down its transmission rate and causing a
Denial of Service.
Affected Systems This traffic should have no adverse impact.
Attack Scenarios An attacker may craft an ICMP "Source Quench" message with an invalid
ICMP code.  A single packet itself is not harmful, but the unusual ICMP
code my indicate that this packet was abnormally generated.
Ease of Attack Simple. There are many packages available to generate ICMP messages.
Corrective Action If a routing device in your network is generating this message, investigate why it does not have a standard ICMP code of 0.
Additional References