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(U) Viruses, Spyware, and Malware: What's the Difference? (PC Magazine, 08 FEB 2011)
(U) A flu virus spreads by infecting your body's cells and turning them into virus-replication factories. In
a similar fashion a computer virus injects its code into an innocent program; when the program runs the
virus code runs too, spreading the virus to other programs or computers. A USC researcher coined the
term "computer virus" back in 1984. These days, though, viruses are just one among many types of
malicious programs you may encounter. Your antivirus software should handle all of them.
(U) Replicating Threats
(U) A virus runs when the user launches an infected program or boots from an infected disk. Viruses keep
a low profile, so as to spread widely without being detected. Most of the time, the virus code simply
infects new programs or disks. Eventually, often at a predefined date and time, the virus payload kicks in.
Early virus payloads were often mindlessly destructive; these days they're more likely to steal information
or implement a DDoS (Distributed Denial of Service) attack against a major web site.
(U) Worms are similar to viruses, but they don't require the user to launch an infected program. Simply
put, the worm copies itself to another computer and then launches that copy. In 1988 the Morris worm,
intended as a simple proof of concept, caused serious damage to the budding Internet. While it wasn't
meant to be malicious, its over-enthusiastic self-replication sucked up a huge amount of bandwidth.
(U) Just as Greek forces fooled the people of Troy by concealing warriors inside the Trojan Horse, Trojan
programs conceal malicious code within a seemingly useful application. The game, utility, or other
application typically performs its stated task, but sooner or later it does something harmful. This type of
threat spreads when users or Web sites inadvertently share it with others.
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(U) Threats Defined by Behavior
(U) Viruses, worms, and Trojans are defined by the way they spread. Other malicious programs take their
names from what they do. Spyware, not surprisingly, refers to software that spies on your computer and
steals your passwords or other personal information. Adware pops up unwanted advertisements, possibly
targeted to your interests by using information stolen by a spyware component.
(U) Rootkit technology hooks into the operating system to hide a malicious program's components. When
a security program queries Windows to get a list of files, the rootkit removes its own files from the list.
Rootkits can also hide entries in the Registry. A bot infestation doesn't actively harm your computer, but
it makes your system complicit in harming others. It quietly hides itself until the owner, or "bot herder",
broadcasts a command. Then, along with hundreds or thousands of others, it does whatever it's told. Bots
are often used to send spam, so the spammer's own systems aren't implicated.
(U) Some malicious programs exist specifically to aid in distribution of other malware. These dropper
programs tend to be tiny and unobtrusive themselves, but they can funnel a steady stream of other
malware onto your computer. A dropper may receive instructions from its remote owner, as a bot does, to
determine which malware it will distribute. The owner gets paid by other malware writers for this
distribution service.
(U) As the name suggests, ransomware holds your computer or your data for ransom. In the most
common form a ransomware threat will encrypt your documents and demand payment before it will
decrypt them. This type of malware is relatively uncommon simply because the perpetrator must stay
visible enough to receive that payment.
(U) Scareware
(U) Not all antivirus programs are what they seem. Some are actually fakes, rogue programs that don't
protect your security and do harm your bank balance. At best these programs offer no real protection; at
worst they include actively harmful elements. They work hard to scare you into paying for registration, so
they're often called scareware. If you do register, you've both wasted your money and handed your credit
card information to crooks. Avoiding scareware gets more and more difficult as the programs get more
refined.
(U) These categories aren't mutually exclusive. For example, a single threat might virus-style, steal your
personal information like spyware, and use rootkit technology to hide itself from your antivirus. A
scareware program is a kind of Trojan, and it might also steal private data.
(U) The term malware encompasses all of these types of malicious software. Any program whose purpose
is harmful is a malware program, pure and simple. Industry groups like the Anti-Malware Testing
Standards Organization (AMTSO) use this term for clarity, but the general public still asks for antivirus,
not anti-malware. We're stuck with the word antivirus. Just remember that your antivirus should protect
you against any and all malware.
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