A team of hackers led by a German encryption researcher has deciphered and published the code used to secure phone calls made over networks using the global system for mobile communications (GSM) standard. Karsten Nohl, who coordinated a team of 24 independent hackers, announced the accomplishment of the feat at the Chaos Communications Congress in Berlin on Wednesday, Dec. 23, The New York Times reported. 

In the article, a spokeswoman for the GSM Association that devised the encryption method and other security experts said the likelihood of using Nohl’s work to listen to a particular cell phone conversation is unlikely and difficult.

About 3.5 billion of the world’s 4.3 billion cellular telephones use the GSM standard, which has been around since the late 1980s.

According to the Times, Nohl cracked the 64-bit A5/1, which was succeeded by the 128-bit A5/3 algorithm in 2007. However, the article also noted that the stronger algorithm is not widely adopted by carriers.

Read the full article from The New York Times.