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Bugs, E-mail Bombs Hinder Mail Servers

By Frank Dabek
Associate News Editor

MIT's e-mail serviceis experiencing two separate problems that are interfering with the delivery of e-mail.

One problem is caused by a bug in sendmail, the program that sends e-mail on Athena workstations. The other problem, which delays e-mail delivery, results from large amounts of identical e-mail being sent maliciously to MIT's e-mail servers, a practice known as "spamming" or "mail bombing."

The sendmail bug, which only affects Sun Microsystemsworkstations, can occasionally delay the delivery of e-mail, said Jonathon Weiss '93, a systems programmer in Information Systems. The problem "doesn't happen extremely regularly, but enough that people have noticed."

The bug is caused when the sendmail program fails to work as designed. It "locks a message and does not unlock it," preventing the message from being sent out from the workstation, Weiss said.

E-mail affected by the bug will not be sent until the workstation where the mail was written is rebooted or the problem is fixed manually. Since Athena workstations "are not rebooted on a regular schedule," the delays could be significant, Weiss said.

A "work around" should be released this term and will limit the delay to around 24 hours, Weiss said. A complete fix will hopefully be available over the summer when a new version of the Athena operating system is installed, he said.

Besides the problems experienced by Athena users in sending mail, an influx of malicious e-mail messages is causing problems for those using e-mail clients like Eudora and TechMail.

"Occasionally, places from outside MIT have been spamming MIT and other sites," said Alicia L. Allen, a consultant at the IS computer helpdesk. These incidents are considered attacks, she said.

MIT's main e-mail server, which runs at mit.edu, crashed four times during the last week as a result of the attacks, said Thomas J. Coppeto, a systems programmer for IS.

As a result of these attacks, the e-mail servers become overloaded and "prevent people from connecting and sending mail," Coppeto said. The problem mainly affects Eudora and TechMail since these clients do not attempt to use servers other than mit.edu, which has been the main point of outside attacks.

Possible solutions to this problem includes automatically filtering mail to remove messages intended to be an attack. "We are getting much better at detecting mail bombs to see that they don't cause an outage," Coppeto said. Filtering is problematic, though, since legitimate e-mail could be removed unknowingly, he said.

Future versions of Eudora that support multiple servers could reduce the problem, Coppeto said. "We're going to change the operating system and hopefully make this problem go away," he said.

E-mail will not be lost as a result of these problems, Coppeto said. "We guarantee that mail is delivered or in case of failure, bounced to the sender," he said. This is only possible as long as the header is intact, he added.

E-mail "might get delayed up to two hours" as a result of the problem, but it will not be lost, Allen said.