Describe a mobile agent and explain how it can be a potential security threat?

$[4]$

A port scanner is a tool useful to an attacker to identify possible vulnerabilities in a potential victim's system. Cite two situations in which someone who is not an attacker could use a port scanner for a non$-$malicious purpose.

$[4]$

Briefly explain the following network threats or security defense in a distributed computing system:

$($i$)$ Buffer Overflow Attack

$($ii$)$ Address Resolution Protocol $($ARP$)$ spoofing

$($iii$)$ Ping of Death $($PoD$)$

$($iv$)$ SQL Injection Attack

$[16]$

Suppose you have a new smartphone and are excited about the range of apps available for it$.$ You read about a really interesting new game that is available for your phone. You do a quick Web search for it and see that a version is available from one of the free marketplaces. When you download and start to install this app, you are asked to approve the access permissions granted to it$.$ You see that it wants permission to "Send SMS messages" and to "Access your address$-$book." Should you be suspicious that a game wants these types of permissions? What threat might the app pose to your smartphone? Should you grant these permissions and proceed to install it$?$ What types of malware might it be $?$

$[12]$

The two types of transport services that the Internet provides to its applications are TCP and UDP. Discuss the main characteristics that separate these services.

$[8]$

Explain why the Google infrastructure supports three separate data storage facilities.

$[6]$