What is Virus and Worm? | About Virus and Worm | Computer Viruses | Difference b\w Virus and Worm.

About virus

Virus.
       Virus in Network and Information security describes malicious software. This malicious software is developed to spread, replicate themselves, and attach themselves to other files. Attaching with other files help to transfer onto other systems.
Worms.
         Worms are capable of replicating themselves. This capability of worms makes them spread on a victim's system very quickly. Worms are propagating in different forms.
Types of Viruses.
          The seven types of viruses are as follows.
1- Boot Sector Virus
2- Direct Action Virus
3- Resident Virus
4- Polymorphic Virus
5- Overwrite Virus
6- Spacefiller Virus
7- Multipartite Virus
Mobile Threats.
          Emerging mobile phone technology, especially Smartphones has raised the focus of attacker over mobile devices. The most common threat to mobile devices are:
1- Data leakage
2- Unsecured Wifi
3- Network Spoofing
4- Phishing Attacks
5- Spyware
Insider Attack.
          An insider attack is the type of attack that is performed on a system, within a corporate network, by a trusted person. Trusted User is termed as Insider. It is authorized to access the network resources.
Botnets.
          A botnet may use for positive intentions but there also some botnets which are illegal and intended for malicious activities. These malicious botnets can gain access to the systems using malicious scripts and codes either by directly hacking the system or through "Spider". Spider program crawls over the internet and searches for holes in security. Attacker remotely controls all bots from Master computer.

Types of Attacks on a System.
OS Attacks.
In OS Attacks, Attackers always search for an operating system's vulnerabilities. If they found any vulnerability in an Operating System, they exploit to attack against the operating system. Some of common vulnerabilities of an Operating system are:
Buffer Overflow Vulnerabilities.
Buffer overflow is one of the major types of Operating System Attacks. It is related to software exploitation attacks. Buffer Overflow causes problems such as Denial of Service (DoS), rebooting, achievement of unrestricted access and freezing.
Bugs in Operating System.
In software exploitation attack and bugs in software, the attacker tries to exploit the vulnerabilities in software.Vulnerability might be a mistake by developer while developing program code. Attackers can discover these mistakes and use them to gain access to the system.
Unpatched Operating System.
Unpatched operating system allows malicious activities, or could not completely block malicious traffic into a system. Successful intrusion can impact severely in form of compromising sensitive information and data loss.