CHICAGO (NewsNation) — Activision has disabled multiplayer on one of its older Call of Duty games as it investigates reports of a virus, according to the Call of Duty Updates Twitter.

The video game publishing company disabled 2009’s Call of Duty: Modern Warfare 2 multiplayer function from Steam, a video game digital distribution website, on Wednesday after receiving multiple reports of a malware issue.

Hackers used a worm — a virus that uses a series of text strings — that spreads automatically throughout online lobbies, according to a report by TechCrunch.

In an online chatroom, players who have claimed to analyze the malware suggested that users run an antivirus on their computers to try to combat the worm.

Activision spokesperson Neil Wood acknowledged the malware, pointing TechCrunch to the tweet posted on the COD Updates account.

While the game was released in 2009, it still has a small online community of players unable to access its multiplayer features.

The malware issue has yet to be resolved.