Graham Ivan Clark (born January 9, 2003) is an American computer hacker, cybercriminal and a convicted felon regarded as the mastermind behind the 2020 Twitter account hijacking.

[2] In 2018, Graham joined OGUsers, a forum dedicated to selling, buying, and trading online accounts, and was banned after four days.

In 2019, at the age of 16, Clark was involved in stealing 164 bitcoins from Gregg Bennett, a Seattle-based angel investor, through a SIM swap attack.

[2] Clark is widely regarded as the "mastermind" of the 2020 Twitter account hijacking,[4][5] an event in which Clark worked with Mason Sheppard and Nima Fazeli to compromise 130 high-profile Twitter accounts to push a cryptocurrency scam involving bitcoin along with seizing "OG" (short for original) usernames to sell on OGUsers.

The Twitter hack began on June 14 when Sheppard and Fazeli assisted Clark in manipulating employees through social engineering.