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Crashes and Error Messages (part 1) - Viruses, Malware, and Spyware

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12/7/2011 9:10:18 AM
Once you start peeking under Windows' hood, you'll notice some of the tools that have been included to help the system run smoothly. Some of these tools actually work, but it's important to know which ones to use and which ones are simply gimmicks.

1. Viruses, Malware, and Spyware

Malware, or malicious software, is a class of software designed specifically to wreak havoc on a computer—your computer. Malware includes such nasty entities as viruses, Trojan horses, worms, and spyware.

If you're experiencing frequent crashing, nonsensical error messages, pop-up advertisements (other than when surfing the Web), or slower-than-normal performance, the culprit may be one of the following types of malware (as opposed to a feature authored by Microsoft):


Viruses

A virus is a program or piece of code that "infects" other software by embedding a copy of itself in one or more executable files. When the software runs, so does the embedded virus, thus propagating the "infection." Viruses can replicate themselves, and some (known as polymorphic viruses) can even change their virus signatures each time to avoid detection by antivirus software.

Unlike worms, defined next, viruses can't infect other computers without assistance from people (a.k.a. you), a topic discussed in detail in the next section. One particular type of virus, a Trojan horse, spreads itself by masquerading as a benign application (as opposed to infecting an otherwise valid file), such as a screensaver or even, ironically, a virus removal tool.


Worms

A worm[12] is a special type of virus that can infect a computer without any help from its user, typically through a network or Internet connection. Worms can replicate themselves like ordinary viruses, but do not spread by infecting programs or documents. A classic example is the W32.Blaster.Worm, which exploited a bug in Windows XP, causing it to restart repeatedly or simply seize up.

[12] * The term worm is said to have its roots in J.R.R. Tolkien, who described dragons in Middle Earth that were powerful enough to lay waste to entire regions. Two such dragons (Scatha and Glaurung) were known as "the Great Worms." The Great Worm, a virus written by Robert T. Morris in 1988, was particularly devastating, mostly because of a bug in its own code. (Source: Jargon File 4.2.0.)


Spyware and adware

Spyware is a little different than the aforementioned viruses and worms, in that its purpose is not necessarily to hobble a computer or destroy data, but rather something much more insidious. Spyware is designed to install itself transparently on your system, spy on you, and then send the data it collects back to an Internet server. This is sometimes done to collect information about unsuspecting users, but most often to serve as a conduit for pop-up advertisements (known as adware).

Many of these advertisements are pornographic in nature, and will make no exceptions for the age or personal preference of those viewing them. The good news is that this type of attack, whether designed to change your default home page, display pop-up ads, or glean sensitive information from your hard disk, is easily stoppable and clearly preventable.


Aside from the ethical implications, spyware can be particularly troublesome because it's so often very poorly written, and as a result, ends up causing error messages, performance slowdowns, and seemingly random crashing. Plus, it uses your computer's CPU cycles and Internet connection bandwidth to accomplish its goals, leaving fewer resources available for the applications you actually want to use.

Now, it's often difficult to tell one type of malicious program from another, and in some ways, it doesn't matter. But if you understand how these programs work—how they get into your computer, and what they do once they've taken root—you can eliminate them and keep them from coming back.

1.1. How malware spreads

Once they've infected a system, viruses and the like can be very difficult to remove. For that reason, your best defense against them is to prevent them from infecting your computer in the first place.

The most useful tool you can use to keep malware off your computer is your cerebral cortex. Just as malware is written to exploit vulnerabilities in computer systems, the distribution of malware exploits the stupidity of users.

Malware is typically spread in the following ways:


Email attachments

One of the most common ways viruses make their way into computers is through spam. Attachments are embedded in these junk email messages and sent by the millions to every email address in existence, for unsuspecting recipients to click, open, and execute. But how can people be that dumb, you may ask? Well, consider the filename of a typical Trojan horse:

kittens playing with yarn.jpg .scr

Since Windows has its filename extensions hidden by default , this is how the file looks to most Vista users:

kittens playing with yarn.jpg

In other words, most people wouldn't recognize that this is an .scr (screensaver) file and not a photo of kittens. (The long space in the filename ensures that it won't be easy to spot, even if extensions are visible.) And since many spam filters and antivirus programs block .exe files, but not .scr files—which just happen to be renamed .exe files—this innocuous-looking file is more than likely to spawn a nasty virus on someone's computer with nothing more than an innocent double-click.

So, how do you protect yourself from these? First, don't open email attachments you weren't expecting, and manually scan everything else with an up-to-date virus scanner (discussed later in this section). Next, employ a good, passive spam filter, and ask your ISP to filter out viruses on the server side.

Where do these email attachments come from, you may ask? As part of their objective to duplicate and distribute themselves, many viruses hijack your email program and use it to send infected files to everyone in your address book. In nearly all cases, these viruses are designed to work with the email software most people have on their systems, namely Microsoft Outlook and Windows Mail (formerly Outlook Express). If you want to significantly hobble your computer's susceptibility to this type of attack, you'd be wise to use any other email software, such as Mozilla Thunderbird (http://www.mozilla.com) or stick with web-based email like Gmail (http://www.gmail.com) or Windows Live Mail (http://mail.live.com).



Infected files

Viruses don't just invade your computer and wreak havoc, they replicate themselves and bury copies of themselves in other files. This means that once your computer has been infected, the virus is likely sitting dormant in any of the applications and even personal documents stored on your hard disk. This not only means that you may be spreading the virus each time you email documents to others, but that others may be unwittingly sharing viruses with you.

One of the most common types of viruses involves macros, small scripts (programming code) embedded in documents. By some estimates, roughly three out of every four viruses is actually a macro written for Microsoft Word or Excel. These macros are executed automatically when the documents that contain them are opened, at which point they attach themselves to the global template so that they can infect every document you subsequently open and save. Both Word and Excel have security features that restrict this feature, but these measures are clumsy and most people disable them so they can work on the rest of their documents. In other words, don't rely on the virus protection built in to Microsoft Office to eliminate the threat of these types of viruses.


Peer-to-peer (P2P) file sharing

Napster started the P2P file-sharing craze years ago, but modern file sharing goes far beyond the trading of harmless music files. It's estimated that some 40% of the files available on these P2P networks contain viruses, Trojan horses, and other unwelcome guests, but even these aren't necessarily the biggest cause of concern.

To facilitate the exchange of files, these P2P programs open network ports and create gaping holes in your computer's firewall, any of which can be exploited by a variety of worms and intruders. And since people typically leave these programs running all the time (whether they intend to or not), these security holes are constantly open for business.

But wait... there's more! If the constant threat of viruses and Trojan horses isn't enough, many P2P programs themselves come with a broad assortment of spyware and adware, intentionally installed on your system along with the applications themselves. Kazaa, one of the most popular file-sharing clients, is also the biggest perpetrator of this, and the likely culprit if your system has become infected with spyware. (Note that other products like Morpheus, BearShare, Imesh, and Limewire do this, too, just in case you were thinking there was a completely "safe" alternative.)


Web sites

It may sound like the rantings of a conspiracy theorist, but even the act of visiting some web sites can infect your PC with spyware and adware. Not that it can happen transparently, but many people just don't recognize the red flags even when they're staring them in the face. Specifically, these are the "add-ins" employed by some web sites that provide custom cursors, interactive menus, or other eye candy. While loading a web page, you may see a message asking if it's OK to install some ActiveX gadget "necessary" to view the page (e.g., Comet Cursor); here, the answer is simple: no.

Just as many viruses are written to exploit Microsoft Outlook, most spyware and adware targets Microsoft Internet Explorer. By switching to a browser like Firefox, you can eliminate the threat posed by many of these nasty programs.



Network and Internet connections

Finally, your network connection (both to your LAN and to the Internet) can serve as a conduit for a worm, the special kind of virus that doesn't need your help to infect your system. Obviously, the most effective way to protect your system is to unplug it from the network, but a slightly more realistic solution is to use a firewall. Vista comes with a built-in firewall, although a router provides much better protection.

1.2. How to protect and clean your PC

The most popular and typically the most effective way to rid your computer of malware is to use dedicated antivirus software and antispyware software. These programs rely on their own internal databases of known viruses, worms, Trojans, spyware, and adware, and as such, must be updated regularly (daily or weekly) to be able to detect and eliminate the latest threats.

Vista is the first operating system to include an antispyware tool, known as Windows Defender (found in Control Panel and shown in Figure 1). The best part about it is that, left to its own devices, Windows Defender will regularly scan your system and even keep its spyware definitions up to date.

Figure 1. Windows Defender is included with Vista to help protect your PC from the myriad of spyware designed to exploit vulnerabilities in Windows


But Vista still doesn't come with an antivirus tool, mostly to appease the companies that make money selling aftermarket antivirus software (which is ironic, since the best tools are free). Following is a list of the more popular antivirus products.


Avast Home Edition (http://www.avast.com)

Freeware, with a slick interface and good feature set.


Avira AntiVir Classic (http://www.free-av.com)

Freeware, with frequent updates, but only average detection rates.


AVG Anti-Virus (http://free.grisoft.com)

Freeware, a popular yet poor-performing antivirus solution.


Kaspersky Antivirus Personal (http://www.kaspersky.com)

Very highly regarded solution with an excellent detection record.


McAfee VirusScan (http://www.mcafee.com)

Trusted and well-established all-around virus scanner with an intuitive interface and few limitations.


Panda Anti-Virus Titanium & Platinum (http://www.pandasecurity.com)

Lesser-known but capable antivirus software.


Symantec Norton AntiVirus (http://www.symantec.com)

Mediocre, slow antivirus software with a well-known name—but beware of its expensive subscription plan to keep virus definitions updated.

Antispyware software is a more complex field, and as a result, you'll have the best luck using multiple tools in addition to Windows Defender. The top antispyware products include:


Ad-Aware Personal Edition (http://www.lavasoft.de)

Ad-Aware is one of the oldest antispyware tools around, but its definitions are still updated frequently. The personal edition is free and very slick, although it's not usually as effective at removing spyware as Spybot or Spysweeper, both discussed next.

When using Ad-Aware, make sure you click Check for updates now before running a scan. Also, to turn off the awful, jarring sound Ad-Aware plays when it has found spyware, click the gear icon to open the Settings window, click the Tweak button, open the Misc Settings category, and turn off the Play sound if scan produced a result option.



Spybot - Search & Destroy (http://www.spybot.info)

Not quite as nice to look at as Ad-Aware, Spybot excels at purging hard-to-remove spyware. And while both Ad-Aware and Spybot remove tracking cookies from Internet Explorer, Spybot supports Firefox as well.


Spy Sweeper (http://www.webroot.com)

This highly regarded antispyware tool, while not free like the first two, is still a welcome addition to any spyware-fighter's toolbox, and can often remove malware that the others miss.

Figure 2. Spybot - Search & Destroy is one of several antispyware tools that can be used in conjunction with Windows Defender to help keep your PC malware-free


So, armed with proper antivirus and antispyware software, there are four things you should do to protect your computer from malware:

  • Place a router between your computer and your Internet connection.

  • Scan your system for viruses regularly, and don't rely entirely on your antivirus program's auto-protect feature (see the next section). Run a full system scan at least every two weeks.

  • Scan your system for spyware regularly, at least once or twice a month. Do it more often if you download and install a lot of software.

  • Use your head! See the previous section for ways that malware spreads, and the next section for some of the things you can do to reduce your exposure to viruses, spyware, adware, and other malware.

1.3. The perils of auto-protect

Antivirus software is a double-edged sword. Sure, viruses can be a genuine threat, and for many of us, antivirus software is an essential safeguard. But antivirus software can also be a real pain in the neck.

The most basic, innocuous function of an antivirus program is to scan files on demand. When you start a virus scanner and tell it to scan a file or a disk full of files, you're performing a useful task. The problem is that most of us don't remember or want to take the time to routinely perform scans, so we rely on the so-called "auto-protect" feature, where the virus scanner runs all the time. This can cause several problems:


Performance hit

Loading the auto-protect software at Windows startup can increase boot time; also, because each and every application (and document) you open must first be scanned, load times can increase. Plus, a virus scanner that's always running consumes memory and processor cycles, even though you're not likely to spend most of your time downloading new, and potentially hazardous, files for it to scan.


Browser and email monitoring

Some antivirus auto-protect features include web browser and email plug-ins, which scan all files downloaded and received as attachments, respectively. In addition to the performance hit, these plug-ins sometimes don't work properly, inadvertently causing all sorts of problems with the applications you use to open these files.


Annoying and obtrusive messages

The constant barrage of virus warning messages can be annoying, to say the least. For instance, if your antivirus software automatically scans your incoming email, you may be forced to click through a dozen or so messages warning you of virus-laden attachments, even though your spam filter will likely delete them before you ever see them. And nearly every antivirus program makes a big show each time it receives definition updates; while it's nice to know the software is doing its job, it would also be nice to have it do it quietly.


False sense of security

Most importantly, having the auto-protect feature installed can give you a false sense of security ("Sure, I'll open it—I have antivirus software!"), reducing the chances that you'll take the precautions listed elsewhere in this section and increasing the likelihood that your computer will become infected. Even if you are diligent about scanning files manually, no antivirus program is foolproof, and is certainly no substitute for common sense.

Now, if you take the proper precautions, your exposure to viruses will be minimal, if not nil, and you will have very little need for the auto-protect feature of your antivirus software. Naturally, whether you disable your antivirus software's auto-protect feature is up to you, but if you keep the following practices in mind, you should be able to effectively eliminate your computer's susceptibility to viruses.

If you don't download any documents or applications from the Internet, if you're not connected to a local network, if you have a firewalled connection to the Internet, and the only type of software you install is off-the-shelf commercial products, your odds of getting a virus are pretty much zero.

Viruses can only reside in certain types of files, including application (.exe and .scr) files, document files made in applications that use macros (such as Microsoft Word), Windows script files (.vbs), and some types of application support files (.dll, .vbx, .vxd, etc.). And because ZIP files can contain any of the aforementioned files, they're also susceptible.

Conventional wisdom holds that plain-text email messages, text files (.txt), image files (.jpg, .gif, .bmp, etc.), video clips (.mpg, .avi, etc.) and most other types of files are benign in that they simply are not capable of being virus carriers. However, things aren't always as they seem. Case in point: the Bloodhound.Exploit.13 Trojan horse (discovered in 2004) involved certain JPG files and a flaw in Internet Explorer (and most other Microsoft products). The bug has since been fixed, but it's not likely to be the last.

Actually, it is possible to embed small amounts of binary data into image files, which means, theoretically, that an image could contain a virus. However, such data would have to be manually extracted before it could be executed; a virus embedded in an image file would never be able to spontaneously infect your system.


You've heard it before, and here it is again: don't open email attachments sent to you from people you don't know, especially if they are Word documents or .exe files. If someone sends you an attachment and you're tempted to open it, scan it manually beforehand, and then refrain from opening it. Most antivirus software adds a context-menu item to all files, allowing you to scan any given file by right-clicking on it and selecting Scan (or something similar).

If you're on a network, your PC is only as secure as the least-secure PC on the network. If it's a home network, make sure everyone who uses machines on that network understands the concepts outlined here. If it's a corporate network, there's no accounting for the stupidity of your coworkers, so you may choose to leave the auto-protect antivirus software in place.

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