On September 11, 2001, New Yorkers were able to connect using text messaging long after the phone lines were tied up and it became nearly impossible to find a prolonged cellular signal. The same was true in other recent emergencies, including the August hurricanes that devastated the Gulf Coast.

Mayor Bloomberg says one of his campaign goals is to devise a way to use the text messaging network to alert New Yorkers of emergencies – from floods to chemical attacks – in their neighborhoods and the neighborhoods where their spouses work, where their children go to school, and where their elderly parents live.

There may be one problem: According to a new study, hackers could inundate wireless networks with text messages, crippling text message capabilities. That, in turn, would deny voice service to millions of people.

The lead researcher, Patrick McDaniel, a professor of computer science and engineering and the co-director of the Systems and Internet Infrastructure Security Laboratory at Pennsylvania State University, said the study could point to serious implications, especially if the wireless network were incapacitated during an emergency.

“It’s almost become the default means of communication for most people,” he said of wireless communication. “It’s used for first responders and emergency services. It has the mobility that is enormously useful in our daily lives. If the cell phone network suddenly became unavailable, it could certainly cause a crisis to become worse.”

The report found that many of the mechanisms currently in use to safeguard the system are “not adequate.”

It recommended a number of solutions, including separating voice and data on the cellular networks so that overloading the system with text messages would not have an impact on voice services. It also suggested changing Internet-based text messaging to make it more difficult for would-be hackers to develop “hit lists” for potential attacks and creating limits to the number of text messages that can be sent at a time.

Mr. McDaniel said solving this problem is possible, but not simple, since there are hundreds of places in the cell phone network at which someone looking to cause harm could inject text messages. On the upside, he said, the federal government and the cell phone companies are aware of the potential problem and considering solutions.

While Mr. Bloomberg’s text messaging idea is a campaign goal, city officials say agencies including the Department of Information Technology and Telecommunications and the city’s Office of Emergency Management are already discussing how the emergency-notification system could be implemented.

The Information Technology and Telecommunications commissioner, Gino Menchini, said, “We’re always looking for different ways we can respond to emergencies.”

Currently, he said, the city would notify New Yorkers of an emergency by working with television and radio stations and by posting information on the city’s Web site. Using text messages would be a backup to the system that’s now in place, not a replacement, he said, adding that the city understands the limitations of text messaging.

Mr. Menchini said that before the city could implement a text message-based emergency alert system, it would need to communicate with cell phone companies about their p and to develop a plan so that the city’s messages wouldn’t overload the networks.

“We’re constantly speaking to the cellular telephone companies,” he said. “This has been added to the agenda. There’s a lot of issues we have with survivability of their networks. This is another component.”

Mr. Menchini said that once those discussions are completed, the new emergency notification system could be up and running “very quickly.” He added: “The mayor wouldn’t have announced it if we didn’t think it was something that has a lot of potential and the prospect to be helpful.”