海角大神

If you鈥檝e recently seen headlines or听听claiming that hackers can get around WhatsApp鈥檚 encryption, don鈥檛 believe the hype.

Last week, the London cybersecurity firm Positive Technologies 听that it had discovered a vulnerability听in a fundamental part of the mobile communications infrastructure that rendered WhatsApp encryption useless.听

Later, however, the company admitted it may have overstated the scope of the problem. Yes,听they say criminals may be able to take over your WhatsApp or Telegram account by exploiting flaws in the Signaling System No. 7 (SS7) network that routes calls and text messages around the world.

"It wouldn鈥檛 render the encryption ineffective, but it would still expose the user to be impersonated, and continue to be impersonated," said Alex Mathews, a spokesman for Positive Technologies. "The whole reason to come out with this angle is to change the way the they are working," referring to WhatsApp and Telegram security settings that he claims don't put enough of an onus on users to verify their identity.

But experts don鈥檛 think that just any hacker can break into your WhatsApp account. They鈥檇 need access to SS7 鈥撎齮ypically controlled by phone carriers and national operators 鈥撎齭pecialized software, the user鈥檚 cellphone number, and the subscriber identity.

What can be exploited, according to Mr. Mathews鈥� team, are security protocols in SS7 that could allow hackers to steal verification codes to register fraudulent accounts. In fact, using a Linux-enabled laptop loaded with SS7 access and specialized software, Positive Technologies said it could impersonate听WhatsApp and Telegram users.

The听Positive Technologies report followed听a widely publicized segment on SS7 vulnerabilities on "60 Minutes," adding to the听hype about flaws in the mobile backbone. On an April episode of the CBS News program, German security researcher Karsten Nohl exploited SS7 鈥撎齱hich transfers mobile traffic from cellphone towers to the Internet 鈥� to snoop on an iPhone belonging to Rep. Ted Lieu (D) of California, reading calls, e-mails, and text messages.

"This can be done either by a telecom operator or by third-parties that manage to co-opt or infiltrate a telecom provider," said Markus Ra, a Telegram spokesman. WhatsApp representatives declined to comment on the research.

Encryption experts agree that the attack found by Positive Technologies could be challenging to pull off.

"I think for the moment, we should not get caught up in the hype," said Matthew Green, an assistant computer science professor at Johns Hopkins University. For a hacker to the mobile backbone, 鈥測ou either have to find some business that鈥檚 really shady or that鈥檚 not doing their homework."

Since most SS7 networks are closed systems and not connected to the open Internet, it has generally proven difficult to get inside the network without proper permits and听sophisticated telecommunications equipment.

But as more businesses are reselling access to the mobile backbone, the US government wants users to stay alert to the threat. After appearing on "60 Minutes," Mr. Lieu called on the House Oversight Committee to investigate flaws in SS7. The Federal Communications Commission also plans to look at a strategy to transition away from the network.

In the meantime, security savvy users have a few options to protect themselves against SS7 attacks. WhatsApp allows users to enable notifications that show changes in contacts鈥� security information, though it鈥檚 not a default setting. Telegram offers two-step verification for accounts, but that鈥檚 not a default either.

The cryptographer that designed WhatsApp鈥檚 encryption protocol says the attacks would do little to stop the service鈥檚 users from communicating in private.

鈥淢an-in-the-middle attacks are possible, and always will be,"听said Moxie Marlinspike, the cryptographer who designed the Signal protocol used to encrypt WhatsApp messages, referring to a type of cyberattack that鈥檚 been used by hackers and intelligence agencies to intercept communications and spy on Internet users.听"This is exactly what end-to-end encryption was built to protect against."

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