Study: Microsoft repeatedly ranks as top US spammer

Microsoft IP addresses were responsible for a big enough volume of spam to top list for the US

Microsoft has topped a list of biggest US spammers for five out of the past 15 months, and for some of those months it ranked No. 1 in the world, according to a University of Texas study to flag the worst offenders in an effort to get them to improve their security.

Based on results culled from spam block lists, researchers found that Microsoft IP addresses were responsible for a big enough volume of spam to top their list for the US in April and May 2011, and in March, April and June of this year, which is the latest ranking, says John S. Quarterman, a senior researcher with the project at the McCombs School of Business at UT Austin.

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The project analyzes raw data about where spam traffic comes from and tracks down what organization owns the offending IP addresses. The raw data is gathered by groups outside UT, and the Microsoft rankings are based on those compiled by Passive Spam Block List.

While Microsoft didn't respond to requests for comment over the past week, Quarterman says one factor in the high volume of Microsoft spam may be that part of it is MSN, the Microsoft portal that includes its ISP. "Its purpose is to let people have access to the Internet, and that means people have their own computers, which may have all sorts of security problems," he says.

Outbound spam from an organization indicates a security problem, Quarterman says, sometimes because machines have been compromised by botnets and sometimes because users have fallen to phishing ploys. Either way, it means security should be tightened up.

The goals of the research project are to reduce spam and improve organizations' security by drawing attention to their rankings in the hopes that public scrutiny and pressure from customers and peers will encourage them to do something about it.

It worked for at least one medical center in California, according to the center's CIO who spoke on the condition of anonymity. The CIO of the center contacted the CSO after it was ranked at the top of the top medical-profession spammers. "The CIO told me, 'Get us off this list,'" the CSO says.

It turns out that certain end users had fallen for phishing emails purporting to come from the medical center's IT staff. The email said they had exceeded their email storage limits and should click on a link to get it increased. The link triggered a popup window that asked for their user names and passwords. Some users complied, and the credentials were used to get the attackers into the mail server via Outlook Web Access. Once there, they used the server to send spam, the CSO says. Educating end users about how to recognize phishing attempts brought down outbound spam from tens of thousands per day at its peak to less than 100 per day, the CSO says. is running experiments with its rankings, says Andrew Whinston, a professor at the Center for Research in Electronic Commerce at the UT business school. For example, it is ranking the biggest spammers in certain countries and publishing the list, but ranking them in other countries but keeping the list private. The experiment is meant to see whether the entities ranked publicly drop off the list faster than those for which there is no public ranking, Whinston says.

The lists could be used for marketing purposes, Quarterman says. A business could note that its rival, for example, appeared repeatedly on the list and use that as a competitive advantage. Or a business that appeared on the list could say it responded quickly and has fallen off the list.

Depending on the results, the research could indicate that legal requirements to publicly post data security stats about businesses could drive them to be more secure, Whinston says. "Then we'd know how to present that information to the public" to have the greatest beneficial impact, he says.

"We're not trying to solve the spam issue," he says. "We're trying to deal with the broader issue of whether companies should publicly report security issues."

(Tim Greene covers Microsoft for Network World and writes the Mostly Microsoft blog. Reach him at and follow him on Twitter!/Tim_Greene.)

Read more about wide area network in Network World's Wide Area Network section.

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