Unix as a Second Language 
by Sandra Henry-Stocker
Sandra Henry-Stocker has been administering Unix systems for more than 18 years. She describes herself as "USL" (Unix as a second language) but remembers enough English to write books and buy groceries. She currently works for TeleCommunication Systems, a wireless communications company, in Annapolis, Maryland, where no one else necessarily shares any of her opinions. She lives on a small farm on Maryland's Eastern Shore.
This blog offers advice for every-day Unix systems administration and some clever ways to approach more challenging problems.
Send comments and suggestions to mailto:bugfarm@gmail.com.
Unix Tip: Grepping on Whole Words
If every time you grep for a specific word or string, you get a pile of lines that don't match what you were looking for, maybe it's time to learn about whole word searching. In today's column, we examine two ways to get what you want, the whole of what you want and nothing but what you want.
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Is Your Web Site Under Attack?
If you have a web site, the answer is undoubtedly "yes". Someone somewhere or, more likely, quite a few someones are attempting to attack your site or the system on which it is running. Assuming hackers have found your site and are testing it for holes that they might crawl through, let's take a look at how you can uncover evidence of their exploits with a quick examination of your web logs.
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Easy Email Filtering with Procmail
Tossing email into the /dev/null bit bucket is fine when you know the account in question will never receive any valid form of email. You can, however, get a much finer degree of control over email and still automate the cleanup of spam by using a tool such as procmail. Procmail is a basic email filter and not nearly as difficult to set up as people imagine. Let's run through the setup and focus on a couple potential stumbling blocks.
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Eradicate Spam from Unix Service Accounts!
There are numerous ways to reduce the amount of spam that you receive. Good email filters can keep you from ever having to deal with the onslaught of stupid offers you never wanted to see, never mind the outright attempts to steal personal information or rope you into some type of scam. I've found that the spammers have become so desperate to increase their spam traffic deliveries that they are sending spam to system accounts such as bin and listen. Instead of trying to bounce this mail back to the senders -- which in less perverted times might have actually worked, I find it's speedier and less consuming of system resources to just pitch the mail into the bit bucket. Here's how this works.
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