Over 3 billion password and email combinations have been compiled into one massive data dump, a treasure trove for hackers that experts have described as the "mother of all leaks".
The list, which was dubbed COMB (Compilation of Many Breaches), is a collection of data from previous breaches and includes passwords from tech giants such as LinkedIn and Netflix.
The scale of the hack means it is likely that most internet users have been affected in some way and users who replicate passwords across multiple sites are particularly at risk.
Tech website BGR described COMB as the "mother of all leaks" and Threatpost reported that the details were made available on a popular hacking forum at the start of this month, with a user asking just US$2 for access.