Security Corner


August 11, 2008  3:42 PM

The Best Way to Avoid Spam

Ken Harthun Ken Harthun Profile: Ken Harthun

In the 1986 hit movie, The Karate Kid – Part II, the kid’s instructor, Mr. Miyagi, uttered this famous line: “Best way to avoid punch, no be there!” Good advice, indeed; it’s one of those universal pieces of truth that’s so obvious, it’s overlooked. The beauty of it is that it can be applied to anything. In this case, I’ll apply it to spam email, the electronic equivalent of a punch: “Best way to avoid spam, no have email address!”

That’s not exactly practical; we all have an email address. Some of us have several of them (at last count, I have at least nine addresses and I’m sure I’ve missed a couple somewhere). In my final installment of the “How to Secure Your Computer” series, “If Spam has You Irate, Obfuscate!” I gave examples of how you can make your email address unreadable by web bots. Well, that can be a bit of work, forcing you to cut and paste, and make other efforts that can quickly become tedious. There’s an easier way.

Enter Mailinator, the completely anonymous email address that you create on-the-fly when you need to enter an email address but don’t want to use your real one. From their site:

How do I create an account at Mailinator? It’s simple, you just send email to it. Temporary accounts are created when email arrives for them. First, you give out the mailinator email address you created, and then you check it. It’s that simple.

Do I have to sign up? No sign-up, you don’t even have to tell Mailinator you’re coming.

It’s a valid, working email address that you can check just by visiting the site. Of course, anyone can check it just by entering the address in the “Check your inbox” box. Not the best of situations, so they fixed it by providing alternate inbox names . In a nutshell, you use the alternate inbox name for your email address when you post it publicly. Anyone who enters the alternate inbox name will simply get a “no messages” message. Pretty slick.

The beauty of Mailinator is that it provides a valid email address; you can download stuff from and subscribe to those sites that require clicking links in confirmation emails without having to worry about exposing yourself to spam. Use the alternate inbox name or even a different email address every time you need one.

Best way to avoid spam, no have email address — or at least use one you can throw away at will. Either way, you avoid the punch and the security risk.

August 8, 2008  3:44 AM

Software for Secure Computing: Secure Browsers

Ken Harthun Ken Harthun Profile: Ken Harthun

Two of the biggest mistakes Microsoft ever made were tying Internet Explorer into the Windows OS and ActiveX. Exploits took advantage of both and some of the nastiest malware ever written entered millions of PCs through these vectors. I’ll be the first to acknowledge that IE7 has enhanced security and MS has taken some of the hooks out of the OS, but the old adage, “Once burned, twice shy” is my operating basis. Yes, you can configure IE to be relatively secure, but it’s more work than the average user is willing to do. Why not just use a browser that’s relatively secure to begin with?

Some things still (unfortunately) require IE, so you’ll have to use it sometimes; but, for everyday use, I don’t recommend it.  Firefox 3 and Opera 9.5 are both inherently more secure than IE. Take your pick. Either way, you’ll be more secure on the Web.


August 5, 2008  1:01 AM

New Article Series: Software for Secure Computing

Ken Harthun Ken Harthun Profile: Ken Harthun

I recently posted the last article in my How to Secure Your Computer series of security maxims (an eBook will be available shortly–stay tuned for details). While editing the book, I realized there’s a wealth of free and Open Source software available that can help anyone from the novice to the professional practice secure computing.

My “Nine Steps to System Security – 2008” (originally posted as “Seven Steps to System Security – 2004“) is the latest iteration of what is essentially the basis of all the maxims. It lays out a plan that’s been proven highly workable and will serve as a rough guide for the sequence of articles in the new series. The maxims will provide additional layers as the series develops.

At last count, there were 26 pieces of software mentioned in the main articles. Many of those will be grouped into a few general categories, but I believe the Software for Secure Computing series will be substantial.

First in the series will be “Software for Secure Computing: Secure Browsers.”


July 31, 2008  3:32 AM

Thwart malware attacks with a hosts file

Ken Harthun Ken Harthun Profile: Ken Harthun

I’m flattered that Windows Secrets took my suggestion and published an article based on it. (Thanks, Scott!) I can’t give you a link because the article is only available to paid subscribers of the newsletter, but I will give you an excerpt:

By modifying the Hosts file yourself, you can prevent anyone using the PC without an administrator account from accessing unwanted sites. Prime candidates for blocking via this method are sites that host advertising, which can sometimes be a conduit for malware, as I explained in my Apr. 17 story.

To block a file served by the DoubleClick ad server, for example, you would add this line to your Hosts file:

127.0.0.1 ad.doubleclick.net

My article on using a hosts file is the basis for this.  Do it. You’ll be safer on the web.


July 29, 2008  10:47 AM

The Lazy Man’s Way to System Security

Ken Harthun Ken Harthun Profile: Ken Harthun

A good many people have responded to my various articles on system security. Most of the feedback has been positive, but many wondered if there might be a simpler approach, some basic things you can do to protect yourself without too much hard work.

You’re in luck. Call it the lazy man’s way to system security; if you install protection against the the three biggest threats to your on-line security–infections by viruses, worms and Trojans, malicious software (spyware, adware, browser hijackers) and crackers who wish to secretly access and control your PC–you’ll be protected from the worst of security problems. One caveat, however: if you go to questionable sites (you know the ones I mean!) and are in the habit of clicking on links in pop-ups and spam emails, you’re out of luck—nothing can help you because you’re inviting infection.

But, for those who generally try to avoid the bad stuff, these are the four bare security essentials: a NAT router; a good antivirus program; a good anti-malware program; and, a good software firewall. Simple, and highly effective for most users.

Before you ask, the answer is yes, you still need a software firewall, even if you already have a NAT router or hardware firewall. Most hardware firewalls are configured to keep bad traffic from getting in, but will let most traffic from your network out, so they don’t keep those sneaky tracking programs from phoning home. A software firewall will at least give you some warning when a program is trying to access the Internet and you can decide whether to allow it. Besides, it gives you an extra layer of protection, just in case.

I highly recommend you read and apply Nine Steps to System Security – 2008, but if you’re feeling a bit lazy today, the four essentials will get you by.


July 27, 2008  4:09 PM

Nine Steps to System Security – 2008

Ken Harthun Ken Harthun Profile: Ken Harthun

It isn’t getting any better on The Wild, Wild Web, despite state and federal government attempts to arrest and prosecute those responsible for electronically-perpetrated criminal acts. Spyware and malware of all kinds are increasingly more stealthy and difficult to remove thanks to rootkit technology. With the advent of Web 2.0 and its emphasis on sharing and collaboration, web-based attacks are more prevalent than ever, especially those that rely on JavaScript and other scripting languages.

CAN-SPAM did little to deter or eliminate spammers, and today the spam problem is even worse thanks to huge botnets run by organized cyber-crime syndicates. Phishing attacks are harder to detect and more frequent. Recently, I spent the better part of two days cleaning up the aftermath of a mass mailer worm infection for one of our clients; their email is still being blocked by some servers. In its September 2005 issue, Consumer Reports said, “One Third Of Net Users Damaged By Malware.” Considering that article is three years old, I’d wager that the number of infected computers has doubled since then.

In my job as a systems engineer for Connective Computing, Inc., I deal with the effects of malware nearly every day. My previous releases of this article, “Seven Steps to System Security – 2004″ , and “Eight Steps to System Security – 2005“, listed the field-proven steps I recommend to everyone I know. It’s been nearly three years since I published the last guide, but those eight steps haven’t changed much; they just need to be brought up to date, and a new step involving disabling scripting in the browser has been added. Computer users still haven’t learned safe surfing practices, however (will they ever?), and must modify their on-line behavior–particularly by applying the first step–for rest of these steps to be truly effective.

Did I mention these things are proven? They are. These are practices have been protecting computer users in homes and businesses for as long as I’ve been using them. This is free advice that’s really worth something:

  1. Repeat after me: I will NEVER, EVER click on any pop-up of any kind – NEVER, EVER. Not even on the “X” (it’s usually safe, but why take the chance?). Use the key combination Alt-F4 instead; it safely closes the current window. In the slimy world of sleaze-ware, “No” means yes, “Cancel” means yes, “Close” means yes – ANY click on a button means yes. So many times users ask, “How did I get that? I clicked ‘no’ when it asked me!” Well, sorry, but you clicked, so they got you. NEVER, EVER CLICK!
  2. Although Internet Explorer 7.0 has enhanced security and has been detached somewhat from the Windows operating system, it is still too big a target. Crackers are still writing malware that exploits IE security flaws. I recommend you use Firefox or Opera to browse the Web. (Some web sites still require IE, so you’ll be forced to use it for those, but you should minimize its use otherwise.) Whatever browser you use, be sure you configure your preferences to block all unwanted pop-ups or install a pop-up killer like the Google Tool Bar. And while you’re at it, re-read #1!
  3. Patch your system. If you’re still running XP, make sure you have at least service pack 2. If you’re a home user, install service pack 3. (I still see systems that are running XP with service pack 1 or 1a, probably because they turned off automatic updates. While some argue against it, I recommend you turn them on.) And be sure to install any recommended security updates and patches for ALL software on your system, – especially Microsoft Office – not just Windows. If you’re running Windows Vista, you benefit from its enhanced security, but you still need to keep ALL of your applications patched. Secunia’s Online Software Inspector is an excellent tool for scanning your system’s applications to discover those that need updates.
  4. Besides installing a NAT router (see How to Secure Your Computer: Maxim #2), run a properly-configured, proven software firewall. Don’t rely only on Windows XP’s built-in firewall – it blocks inbound attacks only (see this article) and it has flaws of its own (see this article). It will not stop back-door trojans, adware, spyware, and the like from “phoning home” with your sensitive information. (See this article for more info.) While Vista’s firewall does offer outbound filtering, it isn’t much better (see this article for more information). My favorites are the Comodo Personal Firewall (free), and the Sunbelt Kerio Personal Firewall (full-featured for 30 days, then runs free in limited-feature mode, $19.95/yr for full version).
  5. Run a good anti-virus program. Choices abound. I have used AntiVir Personal Edition (free) and Grisoft’s AVG (free). Other good ones are Avast! and Comodo AntiVirus.
  6. Run multiple anti-spyware/anti-adware programs and keep them updated. I recommend: a. Spyware Blaster. This free program blocks adware and spyware from installing in the first place and is frequently updated; b. Ad-Aware. Scan weekly, more frequently if you are a heavy surfer; c. Spybot S&D. Run it on the same schedule as Ad-Aware; d. Microsoft’s Windows Defender is an excellent product and is installed by default in Windows Vista. Configure it for real time protection and automatic updates. One of the best commercial anti-spyware applications is Sunbelt Software’s CounterSpy. It is a PC World Best Buy award winner. Comodo BOClean:AntiMalware is also a good one and it’s free.
  7. Run a spam blocker to isolate junk e-mail. Most malware and all phishing attempts rely on spam. You want to isolate this stuff and delete it. NEVER, I repeat, NEVER, EVER click on a link in any e-mail you are not absolutely certain is legitimate. And to be as safe as possible, always type in the address of your bank, credit card companies, and any other site that you want to keep secure. (See #1 above and apply that principle to links, too!) One of the best programs is Open Field Software’s ella for Spam Control. It uses wizards to “train” it to your personal specifications. There are free and paid versions that work with Outlook, Outlook Express. My clients swear by it. Another good program is Sunbelt Software’s iHate Spam.
  8. On Windows XP, set up a restricted user account and use that for routine tasks. Only log on with administrative privileges when you need to install or configure software. This will prevent rogue programs from affecting your system – they won’t be able to install. You can activate the “run as” feature so you can do administrative tasks while logged in as a restricted user. Microsoft Knowledge Base article Q294676 explains how to activate and use this feature. If you are running Vista, you don’t have to worry about this step: User Access Control (UAC) takes care of it.
  9. Finally, disable scripting in your browser. If you use IE (you probably shouldn’t, see Step 2), Tony Bradley gives you an excellent step-by-step procedure to accomplish this. Firefox users have a more elegant solution in the form of an add-on: NoScript. I use it on every PC. Scripts are blocked globally by default, but you can selectively activate them if you trust the site. For example, you can trust the main site’s scripts but keep blocking any advertising or other third party scripts with no ill effects.

While total immunity is impossible – new infections and variations on existing exploits appear daily – these nine steps will help prevent, catch, or clean 98 percent of the junkware out there. As for the other two percent – or if you are already badly infected – you’ll need to hire a geek like me.


July 25, 2008  1:45 AM

Sure-fire Spam Zombie Killer

Ken Harthun Ken Harthun Profile: Ken Harthun

The other day, I got a call from one of my clients who said that their email was bouncing back from people they had always been able to send to. I investigated and found that the error message was to the effect of <hostname.domain #5.5.0 smtp;550 Blocked;Spam/Zombie address listed at spamhaus.org sbl-xbl>.

Well, that was odd, because the client is running a bona fide Exchange server and a check of the server revealed nothing wrong that I could see. Thinking that maybe an employee was infected with a mass-mailer trojan, I blocked all traffic on smtp port 25 from all addresses on the network except the Exchange server.

Running the netstat -an command on my client’s PC revealed 88 connections, all trying to send mail out on port 25, which the firewall was now blocking.

Certainly, you don’t want to get infected by a mass-mailer trojan, but blocking outbound traffic on port 25 from your network is a sure-fire spam zombie killer and will prevent your IP address from getting blacklisted if someone does get infected.Of course, you’ll want to clean up that infection as quickly as possible.


July 22, 2008  12:26 AM

If Spam Has You Irate, Obfuscate!

Ken Harthun Ken Harthun Profile: Ken Harthun

Spam email is not only a nuisance, it’s a security risk. Most of the viruses, worms, and trojans floating around these days are transmitted in one form or another via spam. The threat can be attached directly to the email or it can rely on some subterfuge to get a clueless victim to click on a link to a malicious website. No matter the method used, the bottom line is that if the spammer doesn’t have a proper email address, the spam won’t be delivered.

Spammers get email addresses in various ways, but the primary method is to use a web bot to scrape them from web sites. It’s not hard to do; the Web is called that because everything is tied together through various links. All the bot has to do is hop around the Web, collecting any email addresses it finds along the way. What the bot is looking for is text strings that take the form of xxx@xxx.xxx. It can easily find those and store them in a database, but it can’t tell whether or not that string is a valid address. You can use this to your advantage; if you can prevent Internet criminals from getting your email address, you can stop them cold. How do you do this? Obfuscate! (Definition: make obscure or unclear.)

Bots can’t think; humans can. To you, the string “kengharthunatyahoodotcom” means something; most scraper bots would ignore it. Similarly, “no_spam_kengharthun@yahoo.com” is easily understood by a human; the bot would recognize it as an email address, but it’s not a valid one and any message sent to that address would bounce. This technique is a good way to post your email address in forums, social networking profiles, etc., but what about posting your email address on your home page or web site?

There are plenty of free tools on the Web to obfuscate a valid email address. This email obfuscator converts my Yahoo! email address to a meaningless (to most bots) string of characters (go try it and you’ll see what I mean). When properly entered into the html code of a web page, it looks like this: kengharthun@yahoo.com. Anyone clicking on the link will be able to send an email, but your average bot won’t be able to harvest it. This technique isn’t foolproof; more sophisticated bots may be able to figure it out. But it’s going to make it more difficult for them and you’ll be calmer and more secure as a result.

So, I leave you with Maxim #14 in the How to Secure Your Computer series of articles:

If your email address will be visible to the public, obfuscate it using one of the methods or tools above.

Ken is a Systems Engineer at Connective Computing, Inc. specializing in network and desktop security for small and medium businesses. Ken helps others through his Ask the Geek blog, is a regular contributor to Dave’s Computer Tips newsletter, and is currently working on his first consumer-oriented book on computer security.


July 19, 2008  12:58 AM

Unpatched PC “0wn3d” in Four Minutes or 16 Hours; Which is it?

Ken Harthun Ken Harthun Profile: Ken Harthun

I just love stories like this one. On the one hand, Internet Storm Center researchers say an unpatched PC connected to the Internet will be compromised in less than four minutes. On the other hand, a researcher and co-founder of the German Honeypot Project (GHP), Thorsten Holz, claims the survival time is much higher than 4 minutes and in fact is nearer 16 hours. “Compared to the survival time from the Internet Storm Center [ISC] which is currently below five minutes, we measure a higher survival time,” he said in a post to the project’s blog. The blog has some interesting graphs, one of which shows that survival time is just under 1000 minutes, or about 16 hours.

So, which is it? Do we believe ISC or GHP? I can tell you from experience with my own firewall logs that my IP address is probed for common vulnerabilities about every two minutes, sometimes as often as once per minute. Based on this, I’d be inclined to believe ISC’s estimate. The bottom line is it doesn’t really matter who’s right–we all agree that it’s a bad idea to connect an unpatched PC to the Internet. From the ISC diary:

While the survival time measured varies quite a bit across methods used, pretty much all agree that placing an unpatched Windows computer directly onto the Internet in the hope that it downloads the patches faster than it gets exploited are odds that you wouldn’t bet on in Vegas.  Using a NAT router and a correctly configured personal firewall is the way to go – both these measures help a lot to improve the odds in favor or your PC.

Be careful out there.

Ken is a Systems Engineer at Connective Computing, Inc. specializing in network and desktop security for small and medium businesses. Ken helps others through his Ask the Geek blog, is a regular contributor to Dave’s Computer Tips newsletter, and is currently working on his first consumer-oriented book on computer security.


July 17, 2008  1:07 AM

Windows SteadyState Can Protect Your Family & Your Family Computer

Ken Harthun Ken Harthun Profile: Ken Harthun

A while back, I used the Microsoft Public Access Computer Security Tool, predecessor to Windows SteadyState, to secure a credit union’s public access computer. They wanted to make sure that no one could use the PC do do anything but work with their online banking site. After a short learning curve, I was able to deliver exactly what they wanted. They were impressed and so was I.

The other day, after yet another grueling session of cleaning up a family member’s malware-infested PC, it occured to me that I should just put SteadyState on it and set up several profiles, putting restrictions in place for the kids, leaving things a bit more open for Mom and Dad, and completely locking down a profile for guest users. Check out what you can do with this:

  • Restrict access to programs and settings
  • Return the computer to its original state with Windows Disk Protection
  • Enforce time limits on use of the computer
  • Control what programs show up in the menus

I haven’t teste this idea yet, but it seems to me that Windows Disk Protection alone would be worth a try. You could set up a profile that would allow completely safe surfing for everyone in the household.

I’m going to take a serious look at this, so stay tuned for my report.


Forgot Password

No problem! Submit your e-mail address below. We'll send you an e-mail containing your password.

Your password has been sent to: