The United States' clandestine National Security Agency (NSA) allegedly spied on top civil-military leadership in Pakistan using malware, The Intercept reported.

Malware SECONDDATE allegedly built by the NSA was used by agency hackers to breach "targets in Pakistan’s National Telecommunications Corporation’s (NTC) VIP Division", which contained documents pertaining to "the backbone of Pakistan’s Green Line communications network" used by "civilian and military leadership", according to an April 2013 presentation document obtained by The Intercept.

The file appears to be a 'top secret' presentation originating from the NSA's SigDev division.

SECONDDATE is described as a tool that intercepts web requests and redirects browsers on target computers to an NSA web server. The server then infects the web requests with malware.

The malware server, also known as FOXACID, has been described in earlier leaks made by former NSA contractor Edward Snowden.

SECONDDATE, however, is just one method the NSA allegedly uses to redirect a target's browser to the FOXACID server. Others involve exploiting bugs in commonly used email providers by sending spam or malicious links that lead to the server, The Intercept said.

Another document obtained by The Intercept, an NSA Special Source Operations division newsletter describes how agency software other than SECONDDATE was used to repeatedly direct targets in Pakistan to the FOXACID servers to infect target computers.

The Intercept confirmed the "authenticity" of the SECONDDATE malware by means of a data leak reportedly made by Snowden.

Snowden released a classified top-secret agency draft manual for implanting malware which instructs NSA operators to track their use of a malware programme through a 16-character string ─ the same string which appears in the SECONDDATE code leaked by a group called ShadowBrokers.

ShadowBrokers last week announced that SECONDDATE was part of a group of NSA-built 'cyber weapons' that it was auctioning off.

Although it is unclear how the code for the software leaked and was obtained by ShadowBrokers, The Intercept claims "the malware is covered with NSA's virtual fingerprints and clearly originates from the agency".

The ShadowBrokers auction of SECONDDATE is the first time any full copies of NSA software have been made available to the public.

"The person or persons who stole this information might have used them against us," Johns Hopkins University cryptographer Matthew Green said on the dangers of such software becoming available to the public.

Speaking to The Intercept, Green said that such exploits could be used to target anyone using a vulnerable router. "This is the equivalent of leaving lockpicking tools lying around a high school cafeteria. It’s worse, in fact, because many of these exploits are not available through any other means, so they’re just now coming to the attention of the firewall and router manufacturers that need to fix them, as well as the customers that are vulnerable."

The Intercept has in the past published a number of reports from documents released by Snowden. The site’s editors include Glenn Greenwald, who won a Pulitzer Prize for his work in reporting on the whistleblower’s revelations.