Fighting Spam and Viruses at the Server, Part I
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Mail administration these days has two aspects to the job that can be both thankless and downright brutal: combating spam and viruses. Users moan whenever their mailboxes fill with spam, and whenever you implement a spam-blocking procedure. They cry in pain whenever viruses inundate them with false bounce reports and trick them into breaking their machines. Management comes to you with surveys that quantify how much time and money is lost in productivity due to both problems, demanding fixes, and then they bristle at the solutions you suggest. Somehow, you're supposed to become a spam and virus expert overnight.
Rather than leave you twisting in the wind, this brief series attempts to bring you up to speed on the latest in spam- and virus-blocking techniques, along with helping you to understand why particular solutions touted by some experts are more—or less—desirable than others. The good news is that there are in fact a number of effective measures that can make life much more pleasant for both you and your users. The bad news is that lots of strategies out there actually cause more harm than good.
Ultimately, what you'll find is that the best solutions available all point to the server side of the equation. The key is implementing a solid plan on your mail server(s) while not violating the basic tenet of mail administration: Lose No Mail.
E-mail Hazards
These days, having an E-mail address is a lot like having unprotected sex with strangers—both invite nasty infections that can get participants into a lot of trouble. Today, E-mail is the vector of choice for viruses, worms, Trojans, and various forms of "spyware," which are all generally designed to steal something from the user: login credentials, CPU cycles and bandwidth to broadcast spam and viruses—even the user's very identity (credit card information, banking information, and more). With subject lines as innocent as "pick up your phone," "hey there," or "a question for you," and mail pretending to be from people in the user's address book thanks to forged mail headers, it can be hard for even a computer expert to tell the genuine mail from the dangerous bait.
The worst and most successful of the lot are the so-called "social engineering" tricks, in which the authors of malicious programs use psychological trickery to encourage the recipient to take the bait and execute an attachment. These sneaky little programs are typically disguised as sound files, screensavers, greeting cards, or even patch programs that promise to remove a virus from the user's system. Leaving users on their own to navigate this minefield is just asking for trouble. It can be difficult enough for computer experts.
Of course, even without attachments, E-mail can be dangerous to the end user, if not so much to the mail administrator's precious machines and networks. A lot of the spam making the rounds these days consists of scams and frauds designed by con artists intent on suckering users out of their hard-earned money. Pyramid schemes, "get rich quick in your spare time" scams, and those charming Nigerian letters proposing to make people millionaires (if only they'd help the author launder some nonexistent cash) trick a surprising number of people. More chilling are the "phishing" schemes, where the con artist mocks up a Web page pretending to be a major bank, mortgage broker, or an online e-tailer such as eBay or Amazon.com. From there, the perpetrator uses E-mail to trick people into logging into the fake site with their real credentials. Armed with this information and other personal data gathered "to verify your identity," the con artist then obtains credit in the victim's name, accesses his or her financial assets, and effectively steals the victim's identity.
Finally, in the world of E-mail dangers, there are the "Web bugs." Spammers often place these little beauties in their spam E-mail to track the effectiveness of their campaigns. No, this isn't some slick use of raw text to overcome an E-mail client. It's an HTML trick: Many people have clients that not only support HTML mail, but render the pages by default the moment that the recipient either previews or opens the mail. Instead of attaching the spam's images, the spammers create the Web page to load the pictures from particular Web sites, complete with a tracking code that identifies the reader. This data assures the spammer that the person's E-mail address is valid, and that the user opened his mail. He can then use this information to target this person for more spam, deeming the victim (accurately) to be among the more "vulnerable" to his methods.
So what's a mail administrator to do? Tackle the problem as close to its source as you can. Doing so saves people downstream a lot of time and resources, and cuts down on the potential for human error. Consider that if you have a company with 30 employees and you leave it up to each individual to deal with his or her own spam and virus problem, you've got 30 different chances for chaos. Even if 29 of those employees are savvy and know better than to execute attachments, it only takes one half-awake staffer to make a careless mistake that affects the entire network.
A better approach involves moving the content-filtering task upstream to the mail server, where you can focus more resources on the problem and shield everyone downstream. This action also has the benefit of putting these tasks in the hands of the people who are likely to have the most computer expertise: the mail and network administrators. These people should know more about the dangers of spam and viruses than more casual computer users in the organization, and ought to be vigilant for these problems in the same way that they keep an eye out for intrusion attempts and crashed vital services.
NOTE
It's still a good idea to install anti-virus programs on all the machines on the network, just as a safeguard against something slipping past the mail server, or getting introduced by another means (for example, an infected laptop at a docking station). This kind of layered approach offers the most peace of mind. Many modern E-mail clients even support spam filtering of one sort or another, which can help users to deal with the few unwanted items that do slip through.