The merits of leaving your wireless access point (WAP) open have been discussed and debated at length, especially when it comes to law enforcement. There is a growing belief that file sharers can protect themselves against lawsuits by keeping their wireless access points open. The problem is, it won't necessarily.

A Texas man who was convicted of possessing child pornography tried to use his open WiFi network as a defense, saying that someone else could have used the same network to traffic in pornographic images. The US Court of Appeals for the Fifth Circuit didn't buy his argument and upheld the conviction.

Here's the story: "famclpe," a Yahoo member using an IP address assigned to Javier Perez in Austin, TX, sent an instant message to a New York woman. Sent over Yahoo's network, the IM contained a sexually explicit picture of a minor. The wheels of justice began turning, and after a subpoena was issued, the FBI fingered Perez as the owner of the account in question.

The FBI says it found CDs with child porn in Perez's room, the only one it searched. An open-and-shut case? No, because there's a twist: the Yahoo account used to send the message belonged to a Mr. Rob Ram, according to Yahoo's records. Perez had a roommate named Robert Ramos and an open WiFi connection, but that was not enough to convince a federal judge to keep the seized CDs from being used in his prosecution. Perez entered a conditional guilty plea to the charges and received a sentence of four years and nine months.

During his appeal, Perez focused on his open WAP. Given the fact that anyone within a couple of hundred feet could have been accessing it, it's impossible to say that the original IM originated from him. As a result, the search warrant was issued in error, Perez argued, and his conviction should be thrown out.

Open WAP could equal probable cause

A District Court, and now the US Court of Appeals for the Fifth Circuit, disagreed. In the Appeals Court's opinion, the judges wrote that the evidence seized in the raid should not have been suppressed. In particular, they didn't buy Perez's arguments that a "mere association between an IP address and a physical address is insufficient to establish probable cause" and that the officers' discovering that he had roommates should have led them to extend their search to cover them.

"In this case it is clear that there was a substantial basis to conclude that evidence of criminal activity would be found at 7608 Scenic Brook Drive," wrote the Court. "[T]hough it was possible that the transmissions originated outside of the residence to which the IP address was assigned, it remained likely that the source of the transmissions was inside that residence."

And the big stack of CDs with child pornography on them kind of sealed the deal.

Keeping an open WAP won't always keep you off the hook

Open WiFi networks represent a potential maelstrom of scum and villainy, according to some people. SCO chairman Ralph Yarro recently told the Utah legislature that the state should regulate WiFi networks, even to the point of banning free and unintentionally open networks. (He's also the guy who proposed moving porn off of port 80.) In cases where people have been arrested for leeching off of an open network, one of the justifications given is the possibility that their freeloader could have been using the free access point for illegal activities.

The "my WiFi network was open" defense has even been raised in the context of filesharing. If I have an open WAP, the reasoning goes, then no one can pin the file-sharing on me. That's a risky strategy, due in no small part to the recording industry's reliance on IP addresses to identify its targets. You may be able to demonstrate down the line that it actually was someone else downloading The Carpenters' Greatest Hits over your open network, but doing so may prove to be a very expensive proposition.