The US Justice Department has recovered a majority of the ransom paid by Colonial Pipeline last month to regain access to its network after it was targeted by the DarkSide ransomware group.

The FBI was able to identify a virtual currency wallet used by the hackers and recovered the proceeds from there with a warrant granted by a federal judge in the Northern District of California.

The DoJ said law enforcement was able to seize 63.7 Bitcoins (nearly $2.3 million) by tracing multiple transfers of bitcoin through the Bitcoin public ledger. The amount represents more than half of 75 Bitcoin (approx. $4.4 million) Colonial Pipeline paid to hackers.

The Department of Justice said it obtained a private key to the wallet where hackers stored the funds. However, officials did not explain how they got the key.

The attack on Colonial Pipeline took place on April 29, 2021. The hackers gained access to the company’s network using an unprotected VPN account, according to the cybersecurity firm Mandiant.

Last month, the Transportation Security Administration issued a new cybersecurity policy requiring pipeline operators to report cyberattacks to the government within 12 hours.