bitcoin blackmail btcc ddos attack
Blackmail attempts targeting BTCC is the latest in a series of campaigns by cyber criminalsiStock

Criminals have targeted bitcoin exchange BTCC with DDoS (distributed denial of service) cyberattacks after the firm ignored a blackmail campaign demanding bitcoin ransoms. The China-based exchange instead responded to the campaign by improving its DDoS defences, causing the attackers to cease attempts to disrupt BTCC services.

The first attack came on Thursday (31 December 2015), affecting BTCC's access to its API (application program interface) and other services. Following the DDoS attacks, the anonymous perpetrators sent a ransom email to BTCC asking for 1 bitcoin (current price $432, £292) to be paid to avoid future attacks.

A second attack came on Friday (1 January 2016), according to Cryptocoinsnews, registering at close to 10Gbps. Despite the size of the attack, BTCC still refused to yield to demands and a second ransom request of 10 bitcoins ($4,320, £2,920) was sent, together with a warning of larger and more sustained attacks.

BTCC instead upgraded its servers and improved its DDoS protection service, leading to subsequent attacks having little impact on BTCC's networks. A final demand of 0.5 bitcoins ($216, £146) was made by the blackmailers but after BTCC continued to ignore demands, the attacker send a final message stating: "Do you even speak English?"

The blackmail campaign against BTCC is the latest in a string of attempts made by criminals demanding sums of bitcoin in order to prevent DDoS attacks. Several bitcoin exchanges and mining services have been targeted, including Bitstamp, BTC-e and the now defunct MtGox.

The semi-anonymous nature of the digital currency bitcoin makes it an attractive method of extorting funds from companies and individuals. According to researchers at Recorded Future, bitcoin extortion increased in 2015.

"Bitcoin attracted more miscreants to the space," said Tyler Bradshaw, solutions engineer at Recorded Future. However it is difficult to determine the success of campaigns as firms are often unwilling to reveal whether ransom demands were met.