Polymorphism / Polymorphic code
Polymorphic code allows a program to process objects differently depending on their data type or class, with the ability to redefine methods for derived classes. As a result of this a program can behave differently under different circumstances.
Polymorphic viruses / malware is typically designed to create malicious code and scripts that change the form, including their filename, encryption and compression characteristics. They create modified versions of itself to avoid detection while not altering the same basic routines after every infection. For this reason they are increasingly difficult to detect with anti-malware programs.
Polymorphic viruses are usually distributed via spam, infected sites, or through the use of other malware.
Port scanning
A port scanner is a type of software that checks network ports for the statuses: open, closed and filtered. They are being used by network administrators but by hackers too who scan the network for open ports to try and get access.
A port scanner sends a request to connect to a TCP or UDP port on a computer and records the response, which helps network engineers diagnose network or connectivity issues. Attackers typically try to make their port scans difficult to detect.
There are different techniques to detect port scans like a dedicated port scan detector application or intrusion detection systems (IDS).
Potentially Unwanted Program (PUP)
This is a bit of a grey area: a PUP is a program that often comes with another program or which is pre-installed on a computer. They are also called bundleware or PUAs (Potentially Unwanted Applications). It is not a type of malware in the sense that it doesn't cause harm to the system, but it takes up space and resources while it might never be used. It can also cause obtrusive pop-ups, altered search results, unwanted bookmarks or other intrusive behaviour changing the normal run of a program or website. What makes it different from junkware is that a PUP is always installed with user-consent, it comes as "part of the package". It is "potentially" unwanted because some users might be happy with it and see it as a bonus (which also can happen with junkware).
Mostly these programs come together with another download, they have user-consent for installation because the user didn't uncheck the checkboxes while installing, that showed a message that another program comes with it (for free ofcouse). Always walk carefully through the install-process when you have downloaded an application, a lot of them have PUPs coming with it.
