A vulnerability has been found and corrected in ntop:

The checkHTTPpassword function in http.c in ntop 3.3.10 and earlier
allows remote attackers to cause a denial of service (NULL pointer
dereference and daemon crash) via an Authorization HTTP header
that lacks a : (colon) character in the base64-decoded string
(CVE-2009-2732).

The updated packages have been patched to correct this issue.