2016年12月大学英语四级真题试卷及答案(第三套)

　　Directions：In this section，you are going to read a passage with ten statements attached to it. Eachstatement contains information given in one of the paragraphs.Identify the paragraphfrom which the information is derived.You may choose a paragraph more than once.Each paragraph is marked with a letter.Answer the questions by marking thecorresponding letter on Answer Sheet 2.

　　Can Burglars Jam Your Wireless Security System?

　　A.Any product that promises to protect your home deserves careful examination.So it isn’t surprising thatyou’11 find plenty of strong opinions about the potential vulnerabilities of popular home—security systems.B.The most likely type of burglary(人室盗窃)by far is the unsophisticated crime of opportunity，usuallyinvolving a broken window or some forced entry.According to the FB1.crimes like these accounted forroughly two.thirds of all household burglaries in the US in 2013.The wide majority of the rest were illegal.unforced entries that resulted from something like a window being left open.The odds of a criminal usingtechnical means to bypass a security system are so small that the FBI doesn’t even track those statistics.

　　C.One of the main theoretical home—security concerns is whether or not a given system is vulnerable to beingblocked from working altogether.With wired setups，the fear is that a burglar(人室盗贼)might be ableto shut your system down simply by cutting the right cable.With a wireless setup.you stick battery—powered sensors up around your home that keep an eye on windows。doors，motion，and more.If theydetect something wrong while the system is armed.they’ll transmit a wireless aleft signal to a base station that will then raise the alarm.That approach will eliminate most cord—cutting concerns--but what abouttheir wireless equivalent，jamming?with the fight device tuned to the fight frequency，what’s to stop athief from jamming your setup and blocking that alert signal from ever reaching the base station?

　　D.Jamming concerns are nothing new，and they’re not unique to security systems.Any device that’s built toreceive a wireless signal at a specific frequency can be overwhelmed by a stronger signal coming in on thesame frequency.For comparison.1et’s say you wanted to“jam”a conversation between two people--allyou’d need to do is yell in the listener’s ear.

　　E) Security devices are required to list the frequencies they broadcast on—mat means that a potential thief canfind what they need to know with minimal Googling.They will.however.need to know what systemthey’re looking for.If you have a sign in your yard declaring what setup you use，that’d point them in theright direction，though at that point，we’re talking about a highly targeted，semi—sophisticated attack，andnot the sort of forced—entry attack that makes up the majority of burglaries.It’s easier to find and acquirejamming equipment for some frequencies than it is for others.

　　F)Wireless security providers will often take steps to help combat the threat of jamming attacks.SimpliSafe，winner of our Editors’Choice distinction.utilizes a special system that’s capable of separating incidental RFinterference from targeted jamming attacks.When the system thinks it’s being jammed，it’ll notify you viapush alert(推送警报).From there，it’s up to you to sound the alarm manually.

　　G)SimpliSafe was singled out in one recent article on jamming，complete with a video showing the entiresystem being effectively bypassed with handheld jamming equipment.After taking appropriate measures tocontain the RF interference to our test lab，we tested the attack out for ourselves，and were able to verify that it’s possible with the right equipment.However.we also verified that SimpliSafe’s anti-jammingsystem works.It caught us in the act，sent an alert to my smartphone，and also listed our RF interferenceon the system’s event log.The team behind the article and video in question make no mention of thesystem，or whether or not it detected them.

　　H)We like the unique nature of that software.It means that a thief likely wouldn’t be able to Google how thesystem works.then figure out a way around it.Even if they could，SimpliSafe claims that its system isalways evolving，and that it varies slightly from system to system，which means there wouldn’t be auniversal magic formula for cracking it.Other systems also seem confident on the subject of jamming.Theteam at Frontpoint addresses the issue in a blog on its site，citing their own jam protection software andclaiming that there aren’t any documented cases of a successful jam attack since the company began offeringwireless security sensors in the l980s.

　　I)Jamming attacks are absolutely possible.As said before.with the fight equipment and the right know—how，it’s possible to jam any wireless transmission.But how probable is it that someone will successfully jam their way into your home and steal your stuff?

　　J)Let’s imagine that you live in a small home with a wireless security setup that offers a functional anti—jamming system.First，a thief is going to need to target your home，specifically.Then，he’s going to needto know the technical details of your system and acquire the specific equipment necessary for jamming yourspecific setup.Presumably，you keep your doors locked at night and while you’re away，so the thief willstill need to break in.That means defeating the lock somehow，or breaking a window.He’11 need to be jamming you at this point，as a broken window or opened door would normally release the alarm.S0，too，would the motion detectors in your home，so the thief will need to continue jamming once he’s inside andsearching for things to steal.However.he’11 need to do so without tripping the anti-jamming system，thedetails of which he almost certainly does not have access to.

　　K)At the end of the day，these kinds of systems are primarily designed to protect against the sort ofopportunistic smash—and—grab attack that makes up the majority of burglaries.They’re also only a singlelayer in what should ideally be a many—sided approach to securing your home，one that includes commonsense things like sound locks and proper exterior lighting at night.No system is impenetrable，and none caNPRomise to eliminate the worst case completely.Every one of them has vulnerabilities that a knowledgeablethief could theoretically exploit.A good system is one that keeps that worst—case setting as improbable aspossible while also offering strong protection in the event of a less-extraordinary attack.

　　36.It is possible for burglars to make jamming attacks with the necessary equipment and skill.37.Interfering with a wireless security system is similar to interfering with a conversation.

　　38.A burglar has to continuously jam the wireless security device to avoid triggering the alarm，both inside and outside the house.

　　39.SimpliSafe provides devices that are able to distinguish incidental radio interference from targeted jamming attacks.

　　40.Only a very small proportion of burglaries are committed by technical means.

　　41.It is difficult to crack SimpliSafe as its system keeps changing.

　　42.Wireless devices will transmit signals so as to activate the alarm once something wrong is detected.

　　43.Different measures should be taken to protect one’s home from burglary in addition to the wireless security system.

　　44.SimpliSafe’s device can send a warning to the house owner’s cellphone.

　　45.Burglars can easily get a security device’s frequency by Internet search.