NEW YORK (CNN/Money) - An overwhelming majority of broadband users are leaving their doors wide open for attack by Internet thieves and hackers, an industry study has found.

The report, released by the National Cyber Security Alliance on Tuesday, found that most broadband users lack basic knowledge of protections against the dangers of an always-on connection to the Internet.

The study, conducted last month in the homes of 120 broadband users, showed 86 percent of the users said they keep sensitive health, financial or personal information on their home computers, but only 11 percent said they have safe and securely configured systems.

"A basic broadband connection without protection can be the equivalent of a high-speed sewage pipe into the home, flooding it with viruses, porn, spam and hackers," said Tatiana Gau, America Online's chief trust officer and a member of the alliance.

The study results highlighted a major perception gap on Internet broadband security.

About 40 percent of the users lacked a firewall to protect their computers from intrusion from the outside, though 86 percent said their systems were protected from online threats, the study found.

The study also said that nearly half of the users have young children at home, but only 3 percent said they have parental control to protect their children from pornography.

"It is critical that every broadband user practice safe broadband with, at minimum, a properly configured firewall, updated anti-virus protection, and parental controls," Gau added.

According to the National Cyber Security Alliance, a safe broadband household needs at least three elements listed on the StaySafeOnline.info Web site:

• A properly configured and secure firewall, which prevents computers on a network from communicating directly with external computer systems and acting as a barrier through which all information passing between the networks and the external systems must travel.
• Automatically or regularly updated anti-virus software that scans a computer's memory and disk drives for viruses. If it finds a virus, the application informs the user and may clean, delete or quarantine any files, directories or disks affected by the malicious code.
• If children are present in the household, parental control software that allows parents to regulate what types of online content their children may access, who they communicate with, and how long they spend online.

"Keeping your computer, personal information and your children safe should be taken seriously," said Orson Swindle, commissioner of the Federal Trade Commission. "Not using common-sense precautions like firewalls, virus protection and parental controls is like leaving the door of your house wide open all night."

Keith Nahigian, spokesman for the alliance, said the study was solely funded by AOL, which is owned by CNN/Money's parent AOL Time Warner (AOL: Research, Estimates).