Some improperly secured systems do not protect against dictionary-assisted password guessing attacks.
Many systems do not place limits on the number of incorrect login attempts, possibly allowing an attacker to guess passwords or in the case of SNMP, community strings. Those systems that do not implement a delay between attempts are also subject to rapid brute force attacks from machines. Although many FTP and telnet servers have implemented delays, some POP3 servers do not. This could allow attackers to conduct password guessing attacks against an affected system.
Cisco Systems Cisco Intrusion Prevention System (IPS) 5.1
LEGAL DISCLAIMER The urgency and severity ratings of this alert are not tailored to individual users; users may value alerts differently based upon their network configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.