Co-ownership is a legal arrangement in which two or more people share ownership of the same asset. Each party may hold a defined share, but the asset is still one object or property, so the agreement must spell out who can use it, who can transfer it, and how costs and proceeds are divided. In practice, the paperwork has to match the real arrangement: the contract, invoice, and accounting records should describe the same asset and the same ownership split.
In cyber security, co-ownership shows up with shared cloud accounts, domains, servers, code repositories, and cryptocurrency wallets. It matters because shared control can create weak accountability, privilege confusion, and slower incident response. Attackers often exploit unclear ownership by abusing stale admin access or by taking over an asset that nobody is clearly responsible for. Defenders reduce risk with written authorization, role-based access, MFA, separate keys, audit logs, and regular review of who can change or transfer the asset.