Can bitcoin be hacked?

The bitcoin network has never been hacked. Individual coins that have been poorly secured, have been stolen, and are always at risk unless proper security measures are taken.

The bitcoin network has never been hacked.

The incredible amount of computational power devoted to securing the bitcoin network makes it unlikely that it could ever be victim to a sustained attack that would make the network unusable. 

Individual coins that have been poorly secured, have been stolen, and are always at risk unless proper security measures are taken.

Using strong, redundant security systems such as offline (cold) storage and multisig technology greatly reduces the risk of theft for your coins.