The vast number of valid private keys makes it unfeasible that brute force could be used for that. To be able to spend the bitcoins, the owner must know the corresponding private key and digitally sign the transaction.
The network verifies the signature using the public key. This was when difficulty was much lower, and is no longer feasible. Semi-log plot of relative mining difficulty [d]  Mining is a record-keeping service done through the use of computer processing power. Every 2, blocks approximately 14 days at roughly 10 min per blockthe difficulty target is adjusted based on the network’s recent performance, with the aim of keeping the average time between new blocks at ten minutes. In this way the system automatically adapts to the total amount of mining power on the network.
Mining pool Computing power is often bundled together or “pooled” to reduce variance in miner income. Individual mining rigs often have to wait for long periods to confirm a block of transactions and receive payment.
In a pool, all participating miners get paid every time a participating server solves a block. This payment depends on the amount of work an individual miner contributed to help find that block.
To claim the reward, a special transaction called a coinbase is included with the processed payments. The bitcoin protocol specifies that the reward for adding a block will be halved everyblocks approximately every four years.
Eventually, the reward will decrease to zero, and the limit of 21 million bitcoins [f] will be reached c. Their numbers are being released roughly every ten minutes and the rate at which they are generated would drop by half every four years until all were in circulation. While wallets are often described as a place to hold  or store bitcoins,  due to the nature of the system, bitcoins are inseparable from the blockchain transaction ledger.
A better way to describe a wallet is something that “stores the digital credentials for your bitcoin holdings”  and allows one to access and spend them.