The good news is that this new code represents only a small incremental step in PC attack capability. Programs such as Back Orifice create backdoors on Windows PCs. A component runs in the background, waiting for a TCP connection. Most backdoor infections are in the form of Trojan horses. Screen savers, video games and greeting cards are common on the 'Net, but sometimes a double click results in a surreptitious hostile code installation.
Backdoors listen patiently for connection requests.
Their convenient GUI management interfaces can scan a range of IP addresses, automatically finding exploitable hosts. Virtually every IP address reachable on the Internet is regularly scanned. Firewalls aren't a cure-all for malware. They can reduce successful connection attempts, but hostile code that connects back out from inside a firewall is becoming more common. Fortunately, while covert code continues to proliferate, effective countermeasures do as well.