What a weekend. It brought with it several stock market hacks and a wave of DDoS attacks on Bitcoin sites. For some exchanges this meant the end. 
 

Storing money securely digitally is not easy. That was probably also made clear to around 300 banks, which, according to Kaspersky, fell victim to a large-scale hack that stretched over several years and which may have stolen more than a billion dollars. Allegedly, the hackers took over the computers of bank employees using malware in e-mails. The action could be the biggest bank robbery in history. 
 
As in most cases like this, the Bitcoin scene couldn't resist a bit of malicious joy. However, this only lasted until problems with Bitcoin exchanges became known in fairly quick succession. The following: 
 
Bter.com is (or was?) A Chinese altcoin exchange. According to the website, 7,170 Bitcoin were stolen from the cold wallet with this transaction. Bter has shut down all wallets, temporarily suspended the service and advertised a bounty of 720 Bitcoin for help in getting the Bitcoins back. The big question is: How can it be that something is stolen from a cold wallet that is not in contact with the internet? Bter.com has announced that it is working with the police on an investigation. There was probably a system for the automatic transfer of bitcoins from the cold to the hot wallet, which the hackers exploited. Cold wallets are not just cold wallets.According to letstalksbitcoin, the community's investigations lead to a well-known hacker and fraudster from Switzerland. 

Exco.in, probably also from China, also an Altcoin exchange. According to the exchange, a user “Ambiorx” gained access to all bitcoins on the exchange on February 6th and 10th. Allegedly, the hacker was able to exploit a bug during a DDoS attack to transfer all Bitcoins to his account, whereupon he then exchanged them for as many Nubits and NuShares as were available and then had these and the remaining BTC paid out. The administrators of the site have registered that the hot wallets have been emptied and have therefore filled them with the entire stocks of cold wallets - which were then also withdrawn. Exactly how much was stolen is not known. Exco.in has discontinued the service and will use the remaining funds to pay out the users. 

HitBTC: According to rumors, this Bitcoin and Altcoin exchange from probably Estonia stopped paying out Bitcoin credit for about a day. However, no further information is known about this, there is no comment from hitbtc. However, the exchange has already attracted attention in the past due to a presumably fake volume and it does not seem to be possible to determine its exact owners and exact location. 
There has been a massive wave of DDoS attacks, especially in China on bitcoin sites.According to twitter, Huobi, one of the largest Bitcoin exchanges, suffered a massive DDoS attack, but was able to prevent a security leak from opening. OKCoin, also one of the largest Bitcoin exchanges, was also offline for a short time. A support employee announced via reddit that there were problems with the DDoS protection service provider Cloudflare. Customer credit is not at risk. It seems that this somehow influenced certain institutions and the world decided to create a blockchain bank, more details here https://cryptoine.com/bitwala-receives-eur-4-million-investment-to-found-the-world-s-first-blockchain-bank/ 
 
shapeshift.io was also affected by DDoS attacks. The online wallet HolyTransactions, the altcoin exchange ccedk.com and the bitcoin altcoin exchange cryptorush.in are still under attack. 
 
All in all, this is very unpleasant news. They show once again that altcoin exchanges are not a safe place for bitcoins or other virtual currencies - which is no wonder since it is immensely complicated to run an exchange with so many wallets while the income from trading altcoin is in the Usually rather modest. However, the incidents also show that large and professional exchanges such as Huobi and OKCoin can also withstand harsh attacks.