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The many faces of viruses

Beware programs that seem too good to be true.

Q: What’s the difference between a virus, a worm, and a Trojan horse?

A: A virus is some piece of programming (including “computer code” and macros) that, when executed, causes one or more negative effects on your PC. These negative effects can include the loss of files, reformatting of your hard drive, the transfer of private information over the Internet, and a wide range of other possible effects. Viruses also tend to replicate, infecting other files, which increases the chances of that virus spreading to other PCs via such media as floppy disks, CD-R discs, and Internet file transfers.

A worm is specific kind of virus that typically replicates itself using addressing features of e-mail clients, such as the address book or the sent-mail box. Where many viruses can only be spread via one person sending another person an infected file, worms can spread automatically, without the knowledge or consent of the sender.

The best way to protect your PC or network from viruses and worms is to install antivirus software, make sure that the software is always running in memory, and always keep the software’s virus definition files updated (refer to the antivirus user’s guide for detailed instructions).

Finally, a Trojan horse is a kind of virus that masquerades as a useful piece of software. For example, you may have received messages urging you to download a program that promises to find conflicts on your machine and fix them. It may seem like a useful free service to you. But don’t do it. Instead of checking for bugs and fixing them, it actually finds all of your hidden passwords and installs spyware that captures all your keystrokes. Other Trojan horses may delete files or send your credit card information to some recipient on the Internet (the actual damage depends on the specific Trojan horse).

Unlike other viruses, Trojan horse programs will generally not try to replicate; they simply do their damage. While many antivirus products will scan for known Trojan horse applications, you should avoid any software that suggests impossible results. For example, a utility that promises to increase your 56Kbps modem speed up to 300 percent should be an immediate cause for suspicion. In general, you should not download software unless you have checked it out with a reputable publication that reviews software.

You can learn more about viruses and other rogue software at sites like

Q: Should I reformat my hard drive from time to time?

A: No. There is no need to reformat a hard drive as a routine procedure. The format process creates logical structures on your hard drive that are needed by the operating system’s file storage system. You typically partition and format a hard drive before installing an operating system (or before a second hard drive will be useable by an existing operating system). Once formatted, you should not need to reformat the drive unless a serious problem occurs with the drive’s file system. For example, if the operating system is damaged beyond recovery by a virus (or by using System Recovery under Windows Me/XP), you generally should reformat the drive before reinstalling the OS.

Remember that formatting a hard drive will render all the information on that drive inaccessible, so be sure to create a backup of any important applications or files (if possible) before using the format utility.

Q: How do I make sense of these PC1600 and other PC numbers?

A: It used to be that memory designations reflected the front side bus (FSB) speed of the device. For example, PC100 and PC133 SDRAM ran at FSB speeds of 100MHz and 133MHz respectively. With DDR SDRAM, the idea got a bit convoluted because Double Data Rate (DDR) SDRAM transferred data on both sides of each clock cycle, so a 100MHz clock had the effect of 200MHz on DDR SDRAM. This got to be very confusing as bus speeds continue to increase, so memory manufacturers decided to mark DDR SDRAM devices (and Rambus memory as well) in terms of their bandwidth–the amount of data per second–that the memory device could handle.

A DDR SDRAM module is an 8-byte (64-bit) memory device. At 100MHz, the effective speed is 200MHz, multiplied times 8 bytes, or 1600 million bytes per second (1.6Gbps). This is denoted as PC1600. At 133MHz, the effective speed is 266MHz, or 2128Mbps (2.1Gbps) denoted PC2100. At 166MHz, the effective speed is 333MHz, or 2664Mbps (2.7Gbps) or PC2700. There are even faster DDR SDRAM memory modules today, with companies like Kingston Technologies releasing PC3000 (370MHz effective), PC3200 (400MHz effective), and PC3500 (434MHz effective) modules for gaming and other high-performance computing systems.

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