GEN:SID 1:1545
Message DOS Cisco attempt
Summary This event is generated when potential Denial of Service (DoS) traffic is detected on the network.
Impact Serious. A DoS attack may be underway.
Detailed Information This event indicates that DoS traffic has been detected. An attempt to exhaust resources on a host may be underway leading to the host being unavailable for legitimate use.
Affected Systems  
Attack Scenarios An attacker may attempt to exhaust resources available on a host leading to the host being unable to respond to legitimate requests.
Ease of Attack Simple to Difficult.
Corrective Action Perform proper forensic analysis on the suspected compromised host to discover the means of compromise.

Rebuild a confirmed compromised host.

Use a packet-filtering firewall to block inappropriate traffic to the network to prevent hosts from being compromised.
Additional References