Questões de Concurso

Atenção: As questões de números 16 a 20 baseiam-se no texto abaixo.

    Technology and legal pressure have changed spammers’ terms of trade. They long relied on sending more e-mails from more computers, knowing that some will get through. But it is hard to send 100m e-mails without someone noticing. In 2008 researchers from the University of California at Berkeley and San Diego posed as spammers, infiltrated a botnet and measured its success rate. The investigation confirmed only 28 “sales” on 350m e-mail messages sent, a conversion rate under .00001%. Since then the numbers have got worse.
    But spammers are a creative bunch. KIK of tricking consumers into a purchase, they are stealing their money directly. Links used to direct the gullible to a site selling counterfeits. Now they install “Trojan” software that ransacks hard drives for bank details and the like.
    Spammers also have become more sophisticated about exploiting trust. In few places is it granted more readily than on social-networking sites. Twitter, a forum for short, telegram-like messages, estimates that only 1% of its traffic is spam. But researchers from the University of California at Berkeley and the University of Illinois at Champaign-Urbana show that 8% of links published were shady, with KIIK of them leading to scams and the rest to Trojans. Links in Twitter messages, they found, are over 20 times more likely to get clicked than those in e-mail spam.
    Nor is Facebook as safe as it seems. As an experiment, BitDefender, an online-security firm, set up fake profiles on the social network and asked strangers to enter into a digital friendship. They were able to create as many as 100 new friends a day. Offering a profile picture, particularly of a pretty woman, increased their odds. When the firm’s researchers expanded their requests to strangers who shared even one mutual friend, almost half accepted. Worse, a quarter of BitDefender’s new friends clicked on links posted by the firm, even when the destination was obscured.

(Adapted from http://www.economist.com/node/17519964)

Instruções: Para responder às questões de números 66 a 70 considere o texto a seguir.

    June 16, 2009

      China Orders Patches to Planned Web Filter

    By EDWARD WONG
    BEIJING − A designer of censorship software that the Chinese government requires to be preinstalled on computers sold in China has been ordered to fix potential security breaches in the software, the newspaper China Daily reported Monday. The report was an indication that the government still supports use of the software __[CONNECTOR__ heated debate over it.
    The software, called Green Dam-Youth Escort, has come under attack by many computer users in China for both political and technical reasons.
    Critics say that although the Chinese government insists that the software will be used only to block access to pornography Web sites, the software’s actual use will be to block any site with content deemed politically objectionable, like the Tibet issue or the 1989 Tiananmen killings.
    The government says all computers sold in China must have the software installed by July 1.
    Early reports had indicated that the government might simply require Green Dam to be included on a CD packaged with new computers, so users would have the option to install it. But it became apparent last week that the government was insisting that all computer makers preinstall the software by July 1. Foreign computer makers learned of the directive just three weeks ago and have been asking the Chinese government to reconsider the rules.
    Some computer experts who have studied the software said last week that it was so flawed that it could allow hackers to monitor a user’s Internet activity, steal personal data or plant viruses. One expert, J. Alex Halderman, a computer science professor at the University of Michigan, has posted on the Internet a report on Green Dam’s vulnerabilities.
    Rather than agreeing to scrap the software altogether, the Chinese government has responded to the technical criticisms by ordering that the potential security breaches be eliminated.
    Mr. Halderman said in an interview last week that it had only taken a few hours for him and his students to infiltrate a computer loaded with Green Dam and force it to crash. A skilled hacker could take over the computer to mine personal data or hitch it to other infected machines in a malevolent network known as a botnet, he added.

(Adapted from The New York Times, June 16, 2009)

Instruções: Para responder às questões de números 66 a 70, considere o texto a seguir.

Novelties

    Rogue programs try their best to register at Web sites and then wreak havoc, but a clever puzzle often bars them from entry: a set of distorted, squiggly letters and numbers that people can decipher and type correctly for admission, but that machines still can’t.
    To stay one jump ahead of fraudsters and their
automated programs, researchers are devising more versions of the puzzles, called captchas, to help sites block abuse that includes spam e-mail, illegal postings and skewed online voting.
    Researchers at Google are testing a new captcha that requires people to turn upright randomly rotated images, like that of a parrot perched temporarily upside-down on a leafy branch. The task is a breeze for people [CONNECTOR] hard for machines.
    The new puzzles could be built around a site’s theme - for instance, cartoons at a Disney site, or objects for sale at eBay, said Rich Gossweiler, a senior research scientist at Google who led the team that developed the system. It can be put in place rapidly, he said, and has an almost limitless supply of images. “Our technique expands the vocabulary of captchas” beyond obfuscated characters, he said.
    The program rejects images like those for human faces that computers have already learned to recognize, he said.
    Luis von Ahn, a professor at Carnegie Mellon University and a pioneer in captcha development, has created a free system, called reCaptcha, now used by about 120,000 sites including Ticketmaster, Craigslist, Facebook, Twitter and The New York Times.
    The system has an unusual twist that provides an added benefit to projects that are digitizing books and papers in archives: the source of the wiggly images that people must decipher is not random. The images are drawn from books and other media that are being digitized in mass projects, but that machines haven’t been able to read because, for instance, the page is wrinkled.
    Automatic character recognition lets people who are having the work scanned know which words it cannot read. These are the words that recaptcha farms out and, once they are interpreted, returns to the original document. In this way, word by word, most of the mystery words are deciphered, in this case by humans. “We are digitizing about 25 million words per day by having people type in captchas,” Dr. von Ahn said.

(Adapted from The New York Times, May 24, 2009)