A particular computer virus frequently infects personal computers

Question Type: Complete the passage

Main Point: No virus detection \(\neq\) Virus installation blocked
Missing Info: The virus may be present in a disguised form

A. shortly after it appeared on the Internet, hackers modified the virus in a way that made it more effective - Incorrect. Effectiveness of the virus is not disputed in the argument. Out of context.

B. the virus was able to replicate itself and then send itself to people in the victim's address book - Incorrect. Out of scope.

C. even after the virus had stopped spreading, the backdoors created during the initial infections remained active - Incorrect. Out of scope.

D. the virus was able to disable virus-scanning software and pose as a virus-removal tool - Correct. If the virus disguised itself in the system as a virus removal tool then it it undetected.

E. the virus also altered the victim's operating system in a way that made it difficult to shutdown the computer without cutting off power to the system. - Incorrect. Again this is not relevant to the main point.

Answer: D

A particular computer virus frequently infects personal computers through an email message. Even though virus-scanning software installed on a computer is designed to identify and alarm the user of a virus infection on that computer shortly after it occurs, this particular virus is rarely observed by virus-scanning software. This fact, however, does not mean that the computer's security systems have blocked installation of the virus, because _______________.

We need to find a reason to support the point. Only D fits in as it presents the alternate why the virus is not detected even when it's present.

A particular computer virus frequently infects personal computers through an email message. Even though virus-scanning software installed on a computer is designed to identify and alarm the user of a virus infection on that computer shortly after it occurs, this particular virus is rarely observed by virus-scanning software. This fact, however, does not mean that the computer's security systems have blocked installation of the virus, because _______________.

Which of the following most logically completes the argument?

A. shortly after it appeared on the Internet, hackers modified the virus in a way that made it more effective. OFS - this does not explain why virus is undetected

B. the virus was able to replicate itself and then send itself to people in the victim's address book. OFS - this does not explain why virus is undetected

C. even after the virus had stopped spreading, the backdoors created during the initial infections remained active. OFS - no reason why virus is undetected

D. the virus was able to disable virus-scanning software and pose as a virus-removal tool. Correct

E. the virus also altered the victim's operating system in a way that made it difficult to shutdown the computer without cutting off power to the system. OFS - no reason why virus is undetected

D is the most relevant of all. so D should be answer

Yes, You are right!
Thanks for the explanation!

A. shortly after it appeared on the Internet, hackers modified the virus in a way that made it more effective--- it can still be detected by virus scanning software ,wrong

B. the virus was able to replicate itself and then send itself to people in the victim's address book--- irrelevant

C. even after the virus had stopped spreading, the backdoors created during the initial infections remained active---incorrect

D. the virus was able to disable virus-scanning software and pose as a virus-removal tool--- relevant

E. the virus also altered the victim's operating system in a way that made it difficult to shutdown the computer without cutting off power to the system.[/quote]-- incorrect

OFFICIAL EXPLANATION:

Reading the question: We have seen a fill-in-the-blank question before, in "Auto Body." Such questions may be phrased with or without a printed line signifying the blank. As we discussed in Auto Body, what goes in the blank should be a logical continuation of the prompt. Logical tests tend not to be possible on this type of question, so we will rely on our filter, ideally a prediction.

Creating a filter: how can we predict what goes in the blank? It must not contradict what has come before and it should finish the expression of the idea. The key is that the virus is on the computer even though the scanning software hasn't detected it. We could imagine that there is a defect in the scanner, or an ingenious design to the virus. Note that you are not expected to know anything about IT security for this question. Critical Reasoning questions are designed not to require any outside knowledge. Outside knowledge may still be useful, inevitably, and that's why the questions cover a range of topics. We could decide on the prediction, "The virus has outsmarted the security systems," as our filter.

Applying the filter: Do any answer choices match our prediction? Choice (A) somewhat does, but rather vaguely. Choice (B) doesn't address why the virus wasn't detected. Choice (C) also doesn't seem to address why the virus wasn't detected, though we might be able to read something into the term "backdoor." Choice (D) would definitely constitute outsmarting the security system. Choice (E) involves outsmarting, but not in a way that would necessarily obscure detection. We're left with (D). We confirm the logic: the correct answer must give an explanation for how a virus might have gone undetected by security systems. Choice (D) is the only option. Choice (C) sounds close, but we presume that many viruses possess backdoors and are detected.

The correct answer is (D).

The conclusion: Even though the virus was not detected by the antivirus software, we cannot say that the computer was successful in blocking the installation of the virus.

We have been asked to strengthen the conclusion. So, let us find that answer choice that does strengthen the conclusion.

A. shortly after it appeared on the Internet, hackers modified the virus in a way that made it more effective - we are concerned with the virus that spread through email. (A) does not make it clear whether modified version of this virus has been effective via email or via the whole internet domain. Hence, eliminate (A)

B. the virus was able to replicate itself and then send itself to people in the victim's address book - we are concerned with what happens to a particular computer once it gets infected by the virus. Knowing the fact that the virus has spread to 'other computers' does nothing to strengthen the conclusion drawn. Hence, eliminate (B).

C. even after the virus had stopped spreading, the backdoors created during the initial infections remained active - does this mean that these initial infections can still cause damage? can these initial infections be detected by the antivirus? (C) does not clearly strengthen the conclusion. hence, eliminate (C).

D. the virus was able to disable virus-scanning software and pose as a virus-removal tool - Okay. Now we know a reason why the antivirus was not able to pick up the virus. This strengthens the idea that 'the computer antivirus was not successful in detecting the virus'. Hence, (D) is the right answer choice.

E. the virus also altered the victim's operating system in a way that made it difficult to shutdown the computer without cutting off power to the system. - Irrelevant since it does not strengthen nor weaken the conclusion. Hence, eliminate (E).

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