>> Malware, short for malicious software, is intended to damage or break a computer systemor network without user knowledge or approval.
There are many different types of malwarebut the two most often confused ones are viruses and worms.
Let's start off by defining what a computer program is.
A computer program, also known as software or an application,is a collection of instructions following algorithmsto solve problems or accomplish tasks.
These instructions are executed by the CPU,central processing unit, the brain of the computer.
Difference number one between a virus and a worm, a virus injects itselfinto a program's instructions, so that the CPU will execute the malicious instructionswhen they are reached in the original program.
Just like a biological virus, a computer virus needs a host file to infect and that file hasto be run for the virus to start running.
The infected host file, in addition to a program, could be a data fileor even the boot sector of a hard drive.
The malicious instructions, whenever read, are executed.
However, the malware known as a worm does not infect host files.
It stands alone in its own file.
Difference number two between a virus and a worm, viruses can spread and replicateby themselves to other files on the same machine.
But in order to spread and replicate to other machines on the network and other networksacross the world, some human intervention is required.
One common way this happens is when someone forwards an email attachment.
Worms can propagate all by themselves across networks all around the world.
They exploit vulnerabilities in protocols, networks, and configurations.
Worms can get into your email lists, compose an email, attach themselvesand even make the subject and body of the email sound like it came from a trusted human.
Difference number three between a virus and a worm,viruses always have malicious payload that is meant to execute.
Worms don't need to have any malicious payload.
Think about this, if Harry the hacker sends a picture of a tigerto an important web server, nothing will happen.
If Harry the hacker sends ten, one hundred or even one thousand picturesto an important web server, nothing will happen.
However, if Harry the hacker puts a program on ten thousand user machinesand they each are instructed to place programs on thousands of other machines,when the time comes, Harry the hacker will give the kill signal and all machines knownas zombies in this botnet, robot network, will be sending traffic to a poor victim's serverthat will come to a grinding halt.
This common attack is known as a DDoS, distributed denial of serve attack.
Interestingly enough, a DDoS doesn't goafter the confidentiality or integrity of the CIA model.
It's meant to go after the A, the availability of a system or a network.
转载于:https://www.cnblogs.com/sec875/articles/10452639.html
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