The 'Friends' actor died in October, aged 56, and his X account was recently targeted by hackers trying to hoodwink the public into making donations to them, rather than to the Matthew Perry Foundation.
An Instagram post from the Matthew Perry Foundation explains: "We have received reports that Matthew's official X page has been hacked and is directing users to a fraudulent site soliciting donations via cryptocurrency.
"Please do not donate to this site or share the fraudulent posts on social media.
"MatthewPerryFoundation.org is the only website associated with the Foundation, and we are only accepting donations through this site. (sic)"
The caption on the post reads: "This is the only official Matthew Perry Foundation Instagram account, and we will only ever post official Foundation communications.
"Please report imposter accounts, and do not submit donations through any channel other than MatthewPerryFoundation.org. #MatthewPerry. (sic)"
Matthew was found "unresponsive in the pool at his residence" on October 28, and his death was subsequently ruled an accident from the "acute effects of ketamine".
Matthew's 'Friends' co-stars - including Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc and David Schwimmer - issued a joint statement after his death was announced.
They said at the time: "We are all so utterly devastated by the loss of Matthew.
"We were more than just cast mates. We are a family. There is so much to say, but right now we're going to take a moment to grieve and process this unfathomable loss.
"In time we will say more, as and when we are able. For now, our thoughts and our love are with Matty's family, his friends, and everyone who loved him around the world."