In the Adaptive Security Appliance (ASA) version 7.1(2), HTTP accounting causes constant high CPU usage.
This issue is documented in Cisco bug ID CSSsd72617.
Secure Sockets Layer (SSL) VPN causes the ASA to freeze when a connected user tries to map a drive or browse the network. The ASA shows that 128MB of memory is used when WebVPN is enabled, but no users are connected.
The Access Control List (ACL) used to specify traffic for HTTP accounting must specify the IP pool used for WebVPN. This ACL must not specify all IP addresses. A change to this ACL, in order to specify the IP pool as the source, reduces the CPU utilization to acceptable levels.
As a workaround, upgrade from ASA 7.1(2) to 7.1(2)4. To specify the amount of memory assigned to WebVPN processes, issue the memory-size command under the WebVPN configuration as shown in this example: