A “massive and concerted attack” has been launched by a bot system on numerous bitcoin exchanges, Andreas Antonopoulos has revealed. This has lead to popular exchange Bitstamp putting a temporary halt on all bitcoin withdrawals. Antonopoulos, who is the chief security officer of Blockchain.info, said a DDoS attack is taking Bitcoin’s transaction malleability problem and applying it to many transactions in the network, simultaneously. “So as transactions are being created, malformed/parallel transactions are also being created so as to create a fog of confusion over the entire network, which then affects almost every single implementation out there,” he added.