Virus is a program which can copy itselves & infect the 
system. A spam is an e-mail which consists of 
advertisements, insurance, etc... . It may have come 
without our knowledge as an e- mail.

spam is an unwanted e-mail messages, frequently with 
commercial content, in large quantities to an 
indiscriminate set of recipients.

computer virus is a self replicating program which that can 
crash the system.

Virus comes and deleting in all files in the system(for 
example this is type of disease). but spam is coming in 
particular email. this is unnecessary file.

virus is a programe written to mischief our computers and 
spam a unwant mails that we normally received and contain 
all types of imformations.

Virus is program written by the hacker .It is an EXE file 
and one more when the user execute the file it will destroy 
the information Very Important Resource Under  Siege

whereas spam is sperading the along the network without 
inviting