Some customers of the American telecommunications company Sprint Corporation received an email last week as the company sent a notification of a data breach to an undisclosed amount of network users. Meanwhile T-Mobile, the company which proposed $26 billion purchase of Sprint has to wait until the Justice Department approves the merger.

Recent reports revealed that the hackers behind this data breach have gained access to the customers' online logins and could see all data available in the accounts.

Sprint which is currently under the process of a merger deal with US-based wireless network operator, T-Mobile, whose majority shareholder is the German telecommunications company Deutsche Telekom, explained about the breach in a letter sent out to consumers.

However, the company characterized the breach as not causing "a substantial risk of fraud or identity theft." The credit of information and social security numbers aren't visible in these accounts, but there is other sensitive information that can be used by a cyber attacker.

It should be noted that the identity thief or phisher can access most of the information once he has first and last name of a user, phone number, device type, home address, PIN, billing number, device ID and subscriber ID account number of a customer.

However, it is unknown exactly when the hackers started targeting Sprint or accessing the accounts or for how long they had access. Even though the breach window has been identified to be from June 22 to 25, it is possible that the cybercriminals could have targeted the company earlier too.

Can this affect the M&A deal between T-Mobile and Sprit?

The telecommunication company T-Mobile is maintaining its customer momentum during the waiting period of its $26.5 billion merger with Sprint. It ended the quarter with 83.1 million customers. It should be noted that the discussion of the merger started in 2014.

On Friday the Justice Department called for a press conference, along with Antitrust Division chief Makan Delrahim to "announce a significant merger enforcement action." However, the Antitrust Division has delayed the announcement, as it is trying to convince a coalition of US state attorneys general to drop their opposition to the controversial telecom deal.

But, the cybersecurity incident can pose threats to the proposed merger between T-Mobile and Sprint, who are third and fourth-largest wireless service providers in US respectively.

The most attractive sale pitch of the merger is that it will help the US to quickly develop a 5G network and it is strategically important in terms of the competition against China.