Unrestricted Modem on the Internet
Summary
This vulnerability allows a remote intruder to anonymously dial a phone
associated with a live modem.
Impact
By exploiting this vulnerability, a remote intruder can make long distance
calls, leaving the owner of the line with a potentially high phone bill, and
attack random targets.
Background
In the past, dial-out modems were often placed on one of a UNIX host's
TCP
ports without any protection. This was done to facilitate their use.
New special purpose hardware with built-in protection facilities and
authentication methods like
S/Key and digital tokens, however, has made this practice obsolete.
The Problem
With this vulnerability, a remote intruder can anonymously dial from a
phone associated with a live modem. When an unauthorized user can access
a modem to dial anywhere, they can attack random targets and leave the
modem owner with a potentially high phone bill.
Resolution
To eliminate this vulnerability, prevent Internet access of the modem
by placing it behind a firewall or putting password or other authentication
methods, such as S/Key or digital tokens, on the modem.
Where can I read more about this?
Read a bit more information about this vulnerability by visiting this
site.