ransom attack. The attackers demand payment in Bitcoins (virtual currency). The ransomware
malware can spread via infected software or external storage devices, compromised websites and
malicious email attachments. In a lock screen ransomware attack, the login credentials are
changed by the malware and in a data kidnapping attack, the files on the victim’s computer are
encrypted. Some of the famous ransomware attacks are crypto-locker and WannaCry (Alpcan
and Başar, 2011), (Choudhary, 2018), (Al-Hammadi and Aickelin, 2006).
A botnet is a collection of infected devices in which more than one infected devices such
as PCs, mobile devices, IoT devices, and servers are interconnected with each other .These
infected devices are controlled by the malware. The botnets are generally used to generate attack
traffic for DDoS and send spam emails. The device which is infected by the malware is a part of
the network. These infected devices in the network are controlled by an attack group or a single
attacker. This botnet creates a passage to all security threats. Using this passage or created
vulnerability, any threat can be easily injected into the network or devices (Mtibaa, Harras and
Alnuweiri, 2015), (Campbell, 2009), (McKewan, 2006), (Acharya and Pradhan, 2017).
The Distributed denial-of-service attack happens because of the compromised devices in
the network. These compromised devices are called botnets. These compromised devices are
used to attack a target server or network resource or server. The DDoS attacking tools are usually
send more messages, malicious packets and connection requests to the target. This method is
used to slow down the target. The attackers start to exploit a vulnerability in the network to do
the DDoS attack. The attackers use that vulnerable system or device and make it as a Master
device for doing DDoS attack. This Master device also tries to find other vulnerable systems in
the network and controls them by infecting malware in them or bypassing their authentication
controls. These newly infected devices are called ‘Slave devices’. These master and slave
devices which are controlled by an intruder are called ‘bots’ or ‘zombies’. There are many types
of DDoS attacks available (Widagdo and Lim, 2017). They are volume based attacks, protocol
attacks, and application layer attack. The volume-based attacks include ICMP flood, UDP flood
and other spoofed-packet floods (Balasooriya and Fernando, 2013), (Lee and Hong, 2013), (New
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