Virus: Vital Information Resource under Seize. Virus is an executable program depends on the nature of the virus , it may cause damage of your hard disk contents and interfere normal operation of  your computer. It is loaded onto your computer without your knowledge and run against your wished. Viruses can also replicate themselves.

Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information.

Firewalls can't protect very well against things like viruses or malicious software (malware). There are too many ways of encoding binary files for transfer over networks, and too many different architectures and viruses to try to search for them all. In other words, a firewall cannot replace security-consciousness on the part of your users. In general, a firewall cannot protect against a data-driven attack--attacks in which something is mailed or copied to an internal host where it is then executed.

Alternate Answer:
Properly configured firewalls can limit the propagation of worms - a form of malware.  Typically, firewalls are edge or parameter devices (separates network zones) and most viruses and malware targets end points (user workstations and servers).

Plant-incorporated protectants are pesticidal substances produced and used by the living plant,typically to protect the plant from pests, such as insects, viruses, and fungi. Plant-incorporatedprotectants can occur naturally in plants, or can be introduced into plants through either theconventional breeding of sexually compatible plants or through the techniques of modern biology (e.g.genetic engineering). For example, the Cry proteins from Bacillus thuringensis (Bt) bacteria can beintroduced into plants, which then produce the pesticidal protein and provide the plant with resistanceto Lepidopteran insects (e.g. the European corn borer larvae). Plant-incorporated protectants havealso been referred to as plant-pesticides.

By counting the number of PFUs (Plaque Forming Units) in the agar plate culture of microorganisms containing the virus.

Attnuated immunity

Living modified organism, identical with GMO, means any living organism that possesses a novel combination of genetic material obtained through the use of modern biotechnology.
It can be any biological entity capable of transferring or replicating genetic material, including sterile organisms, viruses and viroids.

both cause harm to human health..but
bacteria is single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered to be plants
virus is an ultramicroscopic (20 to 300 nm in diameter), metabolically inert, infectious agent that replicates only within the cells of living hosts, mainly bacteria, plants, and animals: composed of an RNA or DNA core, a protein coat, and, in more complex types, a surrounding envelope.

viruses are more dangerous than bacteria...