A virus is a malicious computer program that replicates itself by copying into other programs. It can negatively impact computers by causing programs to malfunction or corrupting memory. A Trojan horse appears harmless but allows unauthorized access. To prevent them, keep systems updated, use antivirus software, install a firewall, and be wary of unknown programs. Spyware deceives users by promising features while secretly tracking web activity for ads, violating privacy.

1. VIRUS
• A computer program that is designed to
replicate itself by copying itself into the other
programs stored in a computer. It may be
benign or have a negative effect, such as
causing a program to operate incorrectly or
corrupting a computer's memory.

2. Major Components of Viruses
• Infection code
– This is the part that locates an infectable object (previous
snippet)
• Payload
– Any operation that any other program can do but is usually
something meant to be irratating or possibly destructive.
• Trigger
– Whatever sets it off, time-of-day, program execution by
user.

3. Trojan Horse : Introduction
A Trojan Horse program is a unique form of
computer attack that allows a remote user a
means of gaining access to a victim's machine
without their knowledge.
Trojan Horse initially appears to be harmless,
but later proves to be extremely destructive.
Trojan Horse is not a Virus.

5. Prevention of Trojan Horse Programs
• Install latest security patches for the operating system.
• Install Anti-Trojan software.
– Trojan Hunter
– A- Squared
• Install anti-virus software and update it regularly
• Install a secure firewall
• Do not give strangers access (remote as well as physical) to your computer.
• Do not run any unknown or suspicious executable program just to "check it out".
• Scan all email attachments with an antivirus program before opening it.

6. • Spyware is deceptive software, which promises you a feature
or utility in return forSpywaSpyware is deceptive software,
which promises you a feature or utility in return for secretly
tracking your web surfing habits for advertising purposes.
• Spyware is deceptive software, which promises you a feature
or utility in return for secretly tracking your web surfing habits
for advertising purposes.
• is deceptive software, which promises you a feature or utility
in return for secretly tracking your web surfing habits for
advertising purposes.
• secretly tracking your web surfing habits for advertising
purposes Spyware is deceptive software, which promises you
a feature or utility in return for secretly tracking your web
surfing habits for advertising purposes

7. SPYWARE
• Spyware is deceptive software, which promises you a feature or utility in
return for secretly tracking your web surfing habits for advertising
purposes.
• Why Spyware is bad:
- It is annoying
- It is network intensive
- Violates your privacy
- It is a possible security risk
- Violates your privacy
• It is annoying
• It is network intensive