Study: ISPs should block 'Net attack ports

Internet service providers (ISPs) should take security matters into their own hands by blocking access to communications ports on their customers' computers which are commonly exploited by Internet worms and other malicious programs, according to a SANS Institute report.

Leaving the ports open offers little to customers, while needlessly exposing them to infection and making it more likely that ISPs will be overwhelmed by future virus outbreaks, the report said.

Entitled Internet Service Providers: The Little Man's Firewall, the report was written by Johannes Ullrich, chief technology officer of the SANS Internet Storm Center, which uses a worldwide network of sensors to track virus outbreaks and other events on the Internet.

The report identifies four communications ports that are commonly left open on Microsoft Windows machines so that users on an office or home network can share files between two Windows systems. However, those ports were never intended to be used to access files over an insecure public network like the Internet, Ullrich said. At least one of the ports, 135, was used by the recent W32.Blaster worm to locate and infect vulnerable Windows machines on the Internet.

But the four ports were known as handy access points for loosely secured Windows machines long before Blaster appeared in early August, Ullrich said. "These machines are taken out on a regular basis and used in large scale DDoS (distributed denial of service) attacks," he said. By blocking the ports centrally, ISPs would close an open doorway for attackers without requiring any action by their customers, the report said.

Many ISPs already block some or all of the ports named, while others offer customers free personal firewall software to install on their home computers, according to Ullrich. However, home Internet users often lack the technical knowledge necessary to install and configure a firewall or even install a software patch, he said.

Closing the ports would not protect users from all Internet threats. However, it is a simple step that would remove a common and commonly exploited security hole, Ullrich said. "The idea is to get rid of the bulk of problem, then (ISPs) can deal with the remainder of problems on a case by case basis," he said.

Despite their popularity among virus writers and hackers, the Windows ports are not required to browse the Web or perform other common Internet activities, meaning that the change would be transparent to most ISP customers, Ullrich said.

Customers who wanted to share files between home or office computers could still do so safely, as long as they were not doing so over the public Internet and their network was protected by a firewall, he said.

While feasible for ISPs that serve consumers and for universities, the solution is not right for every ISP, Ullrich acknowledged. ISPs that serve corporate customers or larger, Internet backbone providers could disrupt customers' networks using a blanket approach such as the one advocated in the report, he said. "This (plan) is for the little man or home user that knows how to turn on his computer and use a Web browser, but not much else," Ullrich said.

"I think it's a really good idea," said Richard Smith, an independent security expert in Boston. Plugging the holes centrally would keep many Internet users from unwittingly opening their computers, and their private lives, to the Internet, he said.

"Most users don't want to share their hard drive with the whole Internet and they don't even know they're doing it," he said.

ISPs continue to adhere to an "old school" belief that "you've gotta keep everything (on the Internet) open," Smith said.

Practically, however, there are few reasons to block the ports, he said. In fact, while some ISPs are dragging their feet, ISP America Online is using its firewall feature as a major marketing draw for consumers, Smith said.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Paul Roberts

IDG News Service
Show Comments

Cool Tech

Breitling Superocean Heritage Chronographe 44

Learn more >

SanDisk MicroSDXC™ for Nintendo® Switch™

Learn more >

Toys for Boys

Family Friendly

Panasonic 4K UHD Blu-Ray Player and Full HD Recorder with Netflix - UBT1GL-K

Learn more >

Stocking Stuffer

Razer DeathAdder Expert Ergonomic Gaming Mouse

Learn more >

Christmas Gift Guide

Click for more ›

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

George Khoury

Sharp PN-40TC1 Huddle Board

The biggest perks for me would be that it comes with easy to use and comprehensive programs that make the collaboration process a whole lot more intuitive and organic

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?