Symptoms of virus and worms, types of virus

1. Security Threats and Trends
Module:1
Topic-2:Types of Viruses
By,
Neha Raju K
Assistant Professor
BCA-Cloud Technology and
Information Security Management

2. CONTENTS
Types Of VirusesSymptoms of Computer
Viruses and Worms

3. Symptoms
• Unexpected pop-up windows.
• Unexpected onscreen ads are a typical sign of a virus infection.
• Slow start up and slow performance.
• Suspicious hard drive activity.
• Lack of storage space.
• Missing files.
• Crashes and error messages.

4. Types of Viruses
• Resident Virus
• Direct Action Virus
• Overwrite Virus
• Boot Virus
• Macro Virus
• Directory Virus
• File Infectors
• Companion Virus
• Polymorphic Virus,etc.

5. Resident Virus
File to be
executed Infected file
processing

6. Direct Action
Virus
• This is also called non-resident virus, it gets
installed or stays hidden in
the computer memory.
• It stays attached to the specific type of
files(.exe) that it infect. It does not affect the
user experience and system's performance.
• EX: Vienna virus (variants: Vienna.Choinka,
Vienna.Gympel, Iraqui Warrior,
Vienna.Lisbon,etc.

7. Overwrite Virus
• Virus of this kind is characterised by the fact
that it deletes the information contained in the
files that it infects.
• The only way to clean a file infected by an
overwrite virus is to delete the file completely,
thus losing the original content.
• Examples of this virus include: Way, Trj.Reboot,
Trivial.88.D.

8. Boot Virus
• This type of virus affects the boot sector of a floppy or
hard disk.
• This is a crucial part of a disk, in which information on the
disk itself is stored together with a program that makes it
possible to boot (start) the computer from the disk.
• The best way of avoiding boot viruses is to ensure that
floppy disks are write-protected and never start your
computer with an unknown floppy disk in the disk drive.
• Examples of boot viruses include: Polyboot.B, AntiEXE,
Form, Disk Killer, Michelangelo and Stone virus

9. Macro Virus
• A MAC or Macro virus is a computer virus that
spreads to other computers through software
programs that utilize macros.
• For example, Microsoft Word and Microsoft Excel
are two popular and widely used programs that
are capable of executing macros.
• Examples of macro viruses: Relax Melissa.A, Bablas
and O97M/Y2K.

10. Directory Virus
• Directory viruses change the paths that indicate
the location of a file.
• By executing a program (file with the extension
.EXE or .COM) which has been infected by a
virus, you are unknowingly running the virus
program, while the original file and program
have been previously moved by the virus.
• Once infected it becomes impossible to locate
the original files.

11. File Infectors
• This type of virus infects programs or
executable files (files with an .EXE or
.COM extension).
• The majority of existing viruses belongs
to this category and can be classified
depending on the actions that they
carry out.

12. Companion Virus
• Companion virus can be considered as file infector
virus like resident or direct action types.
• They are known as companion viruses because
once they get into the system they accompany the
other files that already exist.
• Some examples include: Stator, Asimov. 1539 and
Terrax. 1069

13. Polymorphic Virus
• Polymorphic viruses encrypt or encode
themselves in a different way (using different
algorithms and encryption keys) every time
they infect a system.
• This makes it impossible for anti-viruses to find
them using string or signature searches
(because they are different in each encryption)
and also enables them to create a large number
of copies of themselves.
• Examples include: Elkern, Marburg, Satan Bug
and Tuareg.

14. Thank You