The US Department of Justice (DoJ) has granted Box "Authorisation to Operate", allowing employees to use the company's file sharing and information management services.
Box said in an announcement about the deal that the DoJ approved its services after a "rigorous assessment" process that examined security and reliability.
The DoJ will use Box to increase and simplify collaboration between staff and third-party organisations, grant workers mobile access to content and reduce fragmentation and complexity in its IT infrastructure.
Aaron Levie, co-founder and chief executive at Box, explained that the firm won the contract thanks to strong investment in security.
"There is an increasing need to securely connect and enable processes across agencies and jurisdictions as well as to connect government employees with their data, content and stakeholders," he said.
"Innovative government agencies, like the DoJ, are deeply committed to leveraging emerging cloud technologies to better serve the American people, while ensuring the security and privacy of sensitive information.
"We are thrilled to support the DoJ's technology efforts, helping to transform the way they manage and share information."
Box has been working to improve its cloud security and data management services in a bid to allay fears about cloud storage that erupted in 2013 following the Edward Snowden leaks.
The company launched a security-focused Box developer edition of its services in April to help app creators build services securely on the Box platform.
Box also launched a beta Enterprise Key Management encryption service in February for security conscious customers.
Box is one of many cloud storage providers working to improve security in order to target the government sector.
Dropbox's business service was awarded ISO 27018 cloud security certification by EY CertifyPoint earlier in May, following efforts to bolster its defences.
The news follows widespread reports that hackers are using cloud storage services, such as Box and Dropbox, to host and spread malware.
Dropbox struck back against a hacker group using its cloud storage services to store and spread the Bartalex macro malware in April.
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