Viruses have characters of both living and non living organisms.

Characters of living organisms:

1.They have nucleic acid (DNA or RNA) which is their genetic material and hence can replicate

2.They can multiply in the living cells of host

3.They can attack specific hosts

Characters of non living organisms:

1.They can be crystallised

2.They are devoid of cell wall,cell membrane and other cell organelles like ribosomes, mitochondria etc.

3. They remain as inert material outside their hosts

Because of their ability to possess both living and non living characters,they are considered as a link between the two.