From Cisco’s latest security response:
The U.S. Computer Emergency Response Team (US-CERT) has reported a network evasion technique using full-width and half-width unicode characters that affects several Cisco products. The US-CERT advisory is here.
By encoding attacks using a full-width or half-width unicode character set, an attacker can exploit this vulnerability to evade detection by an Intrusion Prevention System (IPS) or firewall. This may allow the attacker to covertly scan and attack systems normally protected by an IPS or firewall.
