Cold storage in the context of Bitcoin refers to storing Bitcoins offline and spending without the private keys controlling them ever being online. This resists theft by hackers and malware, and is often a necessary security precaution especially dealing with large amounts of Bitcoin. For example, a Bitcoin exchange which offers an instant withdrawal feature, and might be a steward over hundreds of thousands of Bitcoins. To minimize the possibility that an intruder could steal the entire reserve in a security breach, the operator of the website keeps the majority of the reserve in cold storage, or in other words, not present on the web server or any other online computer. The only amount kept on the server is the amount needed to cover anticipated withdrawals in one day.