I was just sitting in a lecture when I realized that I had a missed call on my phone. I thought it might be a friend of mine with whom I had arranged lunch later on, but when I checked the number I didn't recognize it. For some reason I had a really weird feeling about the number so I decided to leave my lecture and call it back. On the other side was my credit card company. I couldn't quite follow what was going on at first, but I soon realized that she was asking me if I purchased jewlery for 550€ and some other stuff totaling up to 1000€. I hadn't and so she confirmed that my credit card had been hacked. They've locked the card and are now sending me a new one.
I have no idea how they could've hacked it, I'm pretty sure it's not a security leak from my side. The hackers probably hacked some websites databse, potentially even the credit card company, but that's very unlikely. It is sort of discomforting having one's security breached, but at the same time I'm glad the credit card company was competent enough to pick up on this so quickly and at no cost to myself.
I probably won't take any further measures for now, but I think people should take this to heart and not be negligent about their own security, especially in regard to poker accounts.