An Ohio man will be allowed to sue a web monitoring software maker for breaking US state and federal wiretap laws, the US Court of Appeals has ruled this week.

In 2009, Javier Luis forged an online friendship with Catherine Zang, married at the time to her husband, Joseph Zang.

Even if later it would be proven that the relationship was platonic, Mr. Zang became suspicious of his wife, which led him to purchase a monitoring piece of software called WebWatcher and install it on his wife’s PC.

The husband used the information gathered with WebWatcher to show that his wife engaged in secret conversations with another man, and thus file for divorce and obtain a favorable decision.

During the divorce proceedings, Mr. Luis discovered that he had his private conversations recorded by Mr. Zang and filed a lawsuit, which he later settled.

Mr. Luis also filed a lawsuit against Awareness Technologies (AT), claiming that the company violated the federal Wiretap Act, the Ohio Wiretap Act, and Ohio common law, according to court documents.

AT had its lawyers ask the District Court judge to dismiss the lawsuit, and the judge agreed. AT lawyers said that AT software does not intercept communications in transit, as defined by the law, but after it reaches its destination.

AT’s WebWatcher, according to its website, “records all PC activity including emails, IMs, websites visited, web searches, Facebook/MySpace activity, and anything typed in real time.” This data is then sent to AT servers, where the person who purchased and installed WebWatcher can inspect it.

The company advertises itself as a tool for parents and employers, which allows them to keep an eye on what their kids are doing and how employees spend their time during working hours.

In a 2-1 decision, the US Courts of Appeals has now reversed the initial ruling, meaning Mr. Luis can now sue AT under US wiretap laws. The case has been sent to the District Court to continue regular procedures.

If he wins, this can become a landmark case in which victims of “monitoring software” (also known as spyware) can sue others in civil court.

The case is of great importance for companies that use similar tools to keep employees in check at work, especially when the monitoring tool intercepts private messages.

For these situations, companies would fare better if they used firewalls to block unwanted services instead of deploying monitoring tools.

Additionally, there are also a class of companies that provide semi-legal tools, such as Orcus, which would now become the target of civil lawsuits from spied-on victims.