The KU Leuven SPAM filter

What is SPAM?

SPAM is the collective name for junk email messages sent through the Internet.

Fighting SPAM can sometimes feel like fighting a losing battle. But we can and must continue to do our best to suppress this phenomenon. There are several things you can do yourself, and, of course, KU Leuven will do some of the work.

What can I do myself?

Spam comes in to your email address. This is why it is so important not to simply give your email address to anyone who asks for it. 

It is a good idea to show you some of the ways in which people will try to get hold of your email address:

• people scan web pages, looking for email addresses
• people scan newsgroups, in search of email addresses
• people try to attract users to a web page, where they then require them to enter their email address ("Free cat food, for life!")
• people try to ‘guess’ email addresses: info@domain.be, contact@domain.be, firstname.lastname@domain.be, ...
• people try to lift email addresses from emails that are full of addresses: somebody has forwarded you a forward of a forward of a silly joke, and that email has become full of addresses along the way
• people buy lists of email addresses from other people or from companies that have obtained them with or without respecting the privacy laws

What can you do yourself to combat spammers?

• Be judicious when giving out your email address: Don’t go filling in your email address without thinking about it. If you want to keep your email address free of spam, keep it to yourself, your contacts and your friends.
• Use a special email address with a free provider when filling in online forms: Sometimes there is nothing else for it than to enter your email address on a web page. But don’t use your main email address for this. Use a GMail, Yahoo! or Hotmail address at which you don’t mind receiving junk mail.
• When you post on newsgroups or forums, modify your email address: When you modify your email address you make it hard for automated spammers to find it, but any real person who wants to contact you will be able to derive your real address.
  E.g. sam.spam@hotmail.com becomes sam.spam@DELETETHIS.hotmail.com
• Try wherever possible not to enter your email address to web pages: This is similar to the first tip: be careful when giving out your email address. If you put your email address on a web page you are effectively sharing it with the rest of the world.
• Use the BCC field in your emails: Unfortunately, this is one of those tips that you will need to pass on to friends and contacts if you hope to benefit from it yourself. We have all received mass emails containing jokes or appeals for help, where the whole of the address book can be found in the ‘To’ field. This means that everyone can see the addresses. And it gets worse every time it is Forwarded, if no effort is made to clean the addresses up.
  You can (if you really want to!) send out mass emails without revealing the other recipients to everyone. Put yourself in the ‘To’ field and all the other addresses in the Bcc field (Blind Carbon Copy), and people will see only your address as the receiving address; the others will enjoy a little well-deserved privacy. The best thing, of course, is not to send chain mail. The disadvantage with the BCC field is that nobody will know how widespread a communication is. Netiquette does, however, teach us not to misuse the Bcc field and to use it only when really necessary!
• Never reply to SPAM: Never reply to SPAM by writing a message like "Please stop mailing me". This tells the spammer that you actually read your mail, and that you are the ideal victim for, guess what....? Even more spam!
• Don’t use the Out of Office Assistant for externals unless you really have to: Take care too with holiday messages, Out of Office assistants and automated replies. If you use a holiday message that replies to every email by saying “I’m not here at the moment”, it will also reply to every SPAM. It is important then, to think long and hard about whether you want to automatically inform all those external email senders that you are absent. You are telling the spammers that your email address is active and used.

• Be careful with ‘unsubscribe’ links in spam mail: Always be careful with the 'Unsubscribe' links at the bottom of unrequested mail; these are usually designed to send out even more junk mail.
  An 'unsubscribe' link at the bottom of a requested email (e.g. a newsletter) is usually safe.
• View your mails with the images blocked: The best known email programs (e.g. Outlook) show emails without images as standard. They do this because a spammer can use external images to tell whether or not your email has been actively read. It is best, therefore, to read the email first without images and to download the images only if it comes from a trusted source.
• Never fill in reading confirmations by way of habit: Confirming that you have read an email tells the sender that the email has arrived and has been read. It gives the spammer confirmation that the email address exists and that the mail is actively being read. This increases the chances of even more spam being sent to that address. Therefore, never set your mail client to automatically send out a reading confirmation. At a minimum, see to it that your system asks whether to send a ‘confirmed as read’ message every time you receive and read an email.

What does KU Leuven do?

Every day hundreds of thousands of emails (from over a hundred thousand senders) reach the KU Leuven mail servers from the Internet. That’s quite a heap, and guaranteed to be a heap of nonsense.

At the present time we use several criteria to filter many of these emails, before they even arrive at the user’s address.

• 30% are stopped before they get into KU Leuven by means of a blacklist (one that is not maintained by the university itself)
• of the remaining 70%, about 20% are marked as SPAM, and about 5% are stopped because they contain a virus

To mark email as SPAM, a central SPAM score is automatically generated and assigned to each email. We look at several criteria to assess whether or not an email looks like SPAM.

KU Leuven itself does not stop emails on the basis of the SPAM score, but adds the tag [SPAM?] to the subject if the SPAM score is high.

The central mail server automatically sends email marked as SPAM to the "Junk e-mail (Ongewenste e-mail)" folder.
The email in this folder is automatically deleted after 100 days.

There is nothing that you need do yourself, except look through the Junk e-mail folder now and then to check it doesn’t contain regular mail.