A Brief History of Cybercrime and Cyberwarfare - The Technical and Social History of Software Engineering - page 412

There is a technological race between spam originators and spam defenders.
Hopefully, spam defenses will eventually become sophisticated enough to make
spam disappear as a commercial undertaking. The spam-filtering approaches used
on modern email services are fairly effective, but spam remains a major waste of
human and computer resources.
SQL Injections
The SQL is a popular avenue for hackers. The idea is to create an SQL command
that, if accepted, will perform some harmful act such as passing confidential data
to the hacker. SQL injections are used against websites and databases.
SQL attacks are relatively easy to carry out but also easy to guard against by us-
ing normal, good coding practices that validate inputs including SQL statements.
The SANS Institute provides a good paper by Stuart McDonald on avoiding SQL
attacks. It can be found on the SANS Institute website, www.sans.org .
Trojans
The word “Trojan” harks back to the Trojan horse described in Homer's Iliad . The
original Trojan horse was a giant statue of a horse given as a gift to the Trojans.
Inside, a number of Greek soldiers were concealed. At night after the horse had
been moved into the city of Troy, the hidden solders emerged and opened the city
gates to the Greek army.
In today's computer era, the word “Trojan” means an attractive offering that
conceals a hidden virus or some other nasty payload. A recent prominent Trojan
virus called DNS Changer was front-page news in several papers, so it is worth
considering.
In November 2011, the FBI identified a ring of cybercriminals that had released
the DNS Changer virus. This virus infected about four million computers globally.
Its purpose was to divert clicks on websites to other websites controlled by the
cybercriminals. Apparently, the criminals charged fees for advertising and made
about $14 million from pay-per-clicks until stopped.
In the United States, about half a million computers were infected. This virus
had some unpleasant attributes besides browser hijacking. It also attacked antivir-
us software and kept it from being updated with virus definitions and tools that
could stop the DNS Changer!
What happened after the arrests shows how significant some viruses can be.
After the FBI seized the host computers that had issued the DNS Changer Trojan,