[zizee]

I'm not an expert, this is not expert advice.

AFAIK Trademarks are not automatically an international thing. A business would need to make an effort to register in multiple countries. Trademarks are also not all industries, all at once. McDonald's wouldn't like it, but if my last name was McDonald, and I wanted to setup a lawnmowing business called McDonald's Lawnmowing, they cannot stop me (although you can bet they'd try to scare me off).

I am not sure of your financial position, but it might be economical to register a business name, and even a trademark in your country. This will will give you one more level of protection. They would need to challenge your trademark first. Now, protecting a trademark is not necessarily cheap. It could be a matter of sending a few "piss off" letters in response to their inflated threats, but it could escalate. That said, the same escalation could happen regardless of you having a trademark. Depending on your country, people can (and do) sue other people with no legal standing, and use costs of defending oneself as a cudgel to get what they want.