**4.8 Spyware and adware**

Spyware and adware are software with a common property of collecting personal information of users without their knowledge. Adware is intended to track data of the user's surfing behaviors, and, based on that, pop-ups and advertisements are displayed. The adware clause in the agreement during the

**7**

attacks.

**4.14 Botnets**

*Introductory Chapter: Computer Security Threats DOI: http://dx.doi.org/10.5772/intechopen.93041*

measures, which if followed creates security issues.

antivirus, password sniffing, keylogging, etc.

mugging.

**4.9 Scareware**

**4.10 Rootkit**

**4.11 Keylogger**

details for financial fraud.

as fine to avoid prosecution.

**4.13 Rogue security software**

**4.12 Ransomware**

installation process is often skipped with least seriousness. Spyware on the other hand gets installed on a computer and gathers information about the user's online activities without their knowledge. Spyware contains keyloggers that record everything typed on the keyboard, making it unsafe due to the high threat of identity

Scareware is yet another malware that tricks victims by displaying fake alerts and forcing the victim to buy protective software that is fraudulent. The alerts or the pop-up messages sound like warning messages along with proper protective

Rootkit is a pool of software tools that gets mounted in stealth along with some genuine software. Rootkit allows remote access and administrative control on a system. With these privileges, the rootkit performs malicious activities like disabling of

Keylogger software has the ability to record keystrokes and also capture screenshots and save it to a log file in encrypted form. Keylogger software can record all the information that is typed on the keyboard including passwords, e-mail, and instant messages. The log file created by the keylogger is saved and mailed to the attacker on a remote machine with the motive to extract password and banking

Ransomware is a malicious software that hampers admission to computer or files on the computer. The computers may be locked or files encrypted. Accordingly, the two common types of ransomware are lock screen ransomware and encryption ransomware. The victim will be demanded ransom for the restriction to be removed, and this gets displayed on victim's system. There can also be notification stating that establishments have detected illicit activity on this computer and demands ransom

Rogue security software is another malicious program that deceives users to believe that there is malware installed on their system or the security measures are outdated and hence of concern. They offer installing or updating users' security

A collection of compromised systems or bots acts as a team of infected computers under the control of a bot master to remotely control and send synchronized attacks on a victim host. This army of bots, agents, and bot master constitute a botnet. Botnets are used for sending spams and also for distributed denial of service

settings. Then it is an actual malware that gets installed on the computer.

*Introductory Chapter: Computer Security Threats DOI: http://dx.doi.org/10.5772/intechopen.93041*

installation process is often skipped with least seriousness. Spyware on the other hand gets installed on a computer and gathers information about the user's online activities without their knowledge. Spyware contains keyloggers that record everything typed on the keyboard, making it unsafe due to the high threat of identity mugging.

#### **4.9 Scareware**

*Computer Security Threats*

**4.3 Password attacks**

**4.4 Malware**

**4.5 Virus**

**4.6 Worms**

**4.7 Trojans**

communication network.

hidden from the user.

**4.8 Spyware and adware**

step in password attacks and is automated.

The simplest way to achieve control of a system, or any user account, is through a password attack. If the personal and behavioral details of the victim are known, the attacker starts with guessing password. Frequently, the attacker uses some form of social engineering to trace and find the password. Dictionary attack is the next

After gaining access to a system, the attacker takes the support of malware or malicious software that clandestinely acts against the interests of the computer user.

Computer viruses are the most communal threat to the computer users. Computer viruses are malicious software designed to blow out from one computer to another through file transfer, piggybacks on genuine programs and OS, or e-mails. The email attachments or downloads from particular websites contaminate the computer and also other computers on its list of contacts by using the communication network. Viruses influence the system security by changing the settings, accessing confidential data, displaying unwanted advertisements, sending spam to contacts, and taking control of the web browser [2]. The viruses are identified as

Computer worms are fragments of malicious software that reproduce swiftly and blow out from one computer to another through its contacts, again spreading to the contacts of these other computers and so on and reaching out to a large number of systems in no time. Captivatingly, worms are prepared for spreading by exploiting software vulnerabilities. Worms display unwanted advertisements. It uses up tremendous CPU time and network bandwidth in this process thereby denying access to the systems or network of the victim, creating chaos and trust issues on a

Trojans are programs that appear as perfectly genuine but, in reality, have a malicious part embedded in it. Trojans are spread usually through email attachment from the trustworthy contacts and also on clicking on fake advertisements. The payload of Trojans is an executable file that will install a server program on the victim's system by opening a port and always listening to that port whereas the server is run on the attacker's system. Hence, whenever the attacker wants to login to the victim machine, they can do so by means of the backdoor entry making it

Spyware and adware are software with a common property of collecting personal information of users without their knowledge. Adware is intended to track data of the user's surfing behaviors, and, based on that, pop-ups and advertisements are displayed. The adware clause in the agreement during the

executable viruses, boot sector viruses, or e-mail viruses.

**6**

Scareware is yet another malware that tricks victims by displaying fake alerts and forcing the victim to buy protective software that is fraudulent. The alerts or the pop-up messages sound like warning messages along with proper protective measures, which if followed creates security issues.

#### **4.10 Rootkit**

Rootkit is a pool of software tools that gets mounted in stealth along with some genuine software. Rootkit allows remote access and administrative control on a system. With these privileges, the rootkit performs malicious activities like disabling of antivirus, password sniffing, keylogging, etc.

#### **4.11 Keylogger**

Keylogger software has the ability to record keystrokes and also capture screenshots and save it to a log file in encrypted form. Keylogger software can record all the information that is typed on the keyboard including passwords, e-mail, and instant messages. The log file created by the keylogger is saved and mailed to the attacker on a remote machine with the motive to extract password and banking details for financial fraud.

#### **4.12 Ransomware**

Ransomware is a malicious software that hampers admission to computer or files on the computer. The computers may be locked or files encrypted. Accordingly, the two common types of ransomware are lock screen ransomware and encryption ransomware. The victim will be demanded ransom for the restriction to be removed, and this gets displayed on victim's system. There can also be notification stating that establishments have detected illicit activity on this computer and demands ransom as fine to avoid prosecution.

#### **4.13 Rogue security software**

Rogue security software is another malicious program that deceives users to believe that there is malware installed on their system or the security measures are outdated and hence of concern. They offer installing or updating users' security settings. Then it is an actual malware that gets installed on the computer.

#### **4.14 Botnets**

A collection of compromised systems or bots acts as a team of infected computers under the control of a bot master to remotely control and send synchronized attacks on a victim host. This army of bots, agents, and bot master constitute a botnet. Botnets are used for sending spams and also for distributed denial of service attacks.
