Fighting Spam
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Presentation Transcript
Fighting Spam Randy Appleton Northern Michigan University rappleto@nmu.edu
What is Spam • Probably, it’s “unsolicited and unwanted commercial email sent in bulk”.
Sometimes It’s Not Spam • You did sign up for it. • You accidentally signed up for it. • You still don’t want it.
How Is It Delivered? • Anyone can fake email. • 80% of all spam came from bot-nets • We helped • Open relays are mostly gone. • You can hire this done for you (see Google).
How Much Spam Is There? • In absolute numbers • 1978 - An e-mail spam is sent to 600 addresses. • 1994 - First large-scale spam sent to 6000 bulletin boards, reaching millions of people. • 2005 - (June) 30 billion per day • 2006 - (June) 55 billion per day
How Much Spam Is There #2 • As a percentage of the total volume of e-mail • MAAWG estimates that 80-85% of incoming mail is "abusive email", as of the last quarter of 2005. The sample size for the MAAWG's study was over 100 million mailboxes. • More is coming!!!
Why They Spam • Money • Political causes. • Money • It’s fun • Money • Money
Sell You Something • It’s just mass electronic marketing • They give you a web site, you click over and buy the product. • Email might even be targeted. • weight loss.html
Does Selling By Email Work? • Kodak settled a CAN SPAM suit with the FTC. Their Ofoto unit sent two million commercial messages that didn't comply with the CAN SPAM act. They didn't include a notice that it was an ad, opt-out info, and Kodak's postal address. They paid the FTC $26,000, the revenue they got.
Pure Fraud “There is a sucker born every minute.” • Send email to lots of people. • Wait for sucker to respond. • Convince them to give you money. • Nigerian bank fraud
Identity Theft • Send an email message. • Direct them with a bad URL. • Capture their info. • Reject login and send them to the right site. • Microsoft says to manually check every link.
Identity Theft #2 • An Example • Who Did It.
Stock Manipulation • Pick a small cap stock • Buy some. • Send spam telling people about the stock. • Sell when price rises. • stock-spam.txt • spam-stock.jpg • New York Times
Yes, Spam Works • 5% response rate from sexual material. • 0.02% response rate for drugs. • 0.0075% response rate for Rolex Watches.
Avoiding Spam • Don’t let them get your email address. • Don’t use AOL, etc. • Don’t put address on web page. • Don’t use mailing lists. • Throw away email addresses. • Mailinator, spamgourmet, sneakermail • Annoying …. but possible.
List Removal • For a reputable company, you can always click “remove me from the list”. • A disreputable company will merely take that to be confirmation you’re reading the email. • It’s a calculated gamble.
Auto Detecting Spam • Blacklist • Whitelist • Bayesian Analysis • Other Analysis • These are all things your email server does for you.
Blacklist • A list of web sites from which you don’t take mail. • Automatically interfaced to your email server. • Spamhaus Block List • Zelots • Many choices.
Defeating Blacklists • The spammers can switch ISPs. • The spammers can use a botnet.
Whitelist • There is no global whitelist; you make your own. • Your own contact group is a good start. • Add your institution. • Add people to whom you have sent mail. • Semiautomatic at best.
Bayesian Analysis • Make two piles of mail: spam and ham. • Find words or phrases that can be used to identify mail. • Check all incoming mail for those phrases. • Normally you get a starter database that can be customized.
Example Bayesian Analysis • My friends don’t email me about Viagra. • They do email me about Linux. • The phrase “stupid freshmen” appears in email to me. • The phrase “hot freshman” does not. • Result is a score.
Fighting Back • Don’t. • The nasty email goes to an innocent. • Or it confirms you exist. • Or it bounces back to you.
Using • Gmail filters. • Gmail allows pop downloads. • You can even forward the mail to Gmail to keep your old account name.
