All GSM phones, such as those that run on T-Mobile and AT&T in the United States, are vulnerable to a major security flaw that could allow hackers to send text messages or place phone calls remotely using a new security flaw, one hacker said recently. Speaking to Reuters ahead of a hacking convention in Berlin, Karsten Nohl, the head of Germany’s Security Research Labs, said the attack could be initiated on a large scale, too. “We can do it to hundreds of thousands of phones in a short timeframe,” Nohl explained. “None of the networks protects users very well.” Nohl didn’t provide details on how hackers could take advantage of the flaw, although Reuters said it’s likely that those attending the conference will try to recreate it themselves. Nohl also explained that carriers can easily patch the security hole and that some simply need to update their software. “Mobile network is by far the weakest part of the mobile ecosystem, even when compared to a lot attacked Android or iOS devices,” Nohl said, noting that Germany’s T-Mobile and France’s SFR wireless carriers are the most secure against hackers.