The UK intelligence agency GCHQ has developed sophisticated tools to manipulate online polls, spam targets with SMS messages, track people by impersonating spammers and monitor social media postings, according to newly-published documents leaked by NSA whistleblower Edward Snowden.

Among the programs revealed in the document are:

• GATEWAY: the "ability to artificially increase traffic to a website".

• CLEAN SWEEP which "masquerade[s] Facebook wall posts for individuals or entire countries".

• SCRAPHEAP CHALLENGE for "perfect spoofing of emails from BlackBerry targets".

• UNDERPASS to "change outcome of online polls".

• SPRING BISHOP to find "private photos of targets on Facebook".