HBO has been tracking down Internet users whose connections were used to share and download Game of Thrones Season 5 episodes that leaked last week, according to recent reports.

It can be recalled that just a day before the Game of Thrones Season 5 premiere hit the TV screens, four of its episodes had leaked online to various torrent sites. The source of the leak hasn't been identified, but it has been claimed the leaked episodes have come from a reviewer who received preview copies of the episodes in advance, according to Huffington Post.

"Sadly, it seems the leaked four episodes of the upcoming season of 'Game of Thrones' originated from within a group approved by HBO to receive them," the cable TV network said in a statement. "We're actively assessing how this breach occurred."

By Sunday, March 12, the unexpected Game of Thrones leak led to huge file sharing activity on the world's most popular torrent sites, such as The Pirate Bay, Kickass Torrents and EZTV, reported Tech Times. The countries accounting for the highest number of downloads include the US, UK, India, Canada and France, the site added.

While HBO has not taken legal action yet, it has been reported the company has sent "thousands of warnings" to those subscribers involved in the illegal sharing of the leaked episodes. Over the past week, the cable and satellite TV network sent out countless takedown notices to online users who shared the episodes in public, according to TorrentFreak. The site claimed it has seen several notices, which all come in standard format.

Through IP-Echelon, HBO's anti-piracy partner, the company is reportedly telling Internet providers to "contact the subscriber who has engaged" in the leak and to "take appropriate action against the account holder," TF wrote.

However, since the identities of the alleged pirates are not identified, HBO cannot take strict legal action against the affected subscribers, but it hopes the warnings will prevent people from downloading future episodes.