In its strictest sense, it can be defined as a set of rules or a combination of symbols that have a given value within an established system.
DNS servers, are those computers in which these names are handled (resolved) and associated to their corresponding IPs.
After the computer has been infected, the original file will be unusable.
By doing this, they make it difficult for antiviruses to detect them. These viruses can ‘carry’ other malicious code in the same way that other types, such as polymorphic viruses, do.
The difference between packaging and compression are the tools used. For example, a tool called tar is normally used for packaging , while zip or gzip -WinZip- are used for compressing.