I'm not going to comment on the dangerous aspect, but the unethical aspect is tricky." DDOS the Russian MoD, probably fine on the surface (but maybe not, I'll get to that in a minute). DDOS the Russian's Children's Clinical Hospital, also a government site, definitely unethical.

This then raises another question, does the latter in fact depend on services provided by the former, or a similar government site that has been DDOS'd? This is possible, perhaps they are even cohosted in a data centre somewhere and taking down one will take down another.

Assuming you go ahead then at this point you are basically engaged in attacking the infrastructure (possibly civilian) of a foreign nation at a time of war, presumably from a NATO country. Now you're doing this as a private individual, and your government would probably dissavow any knowledge of your actions, but there's always the chance that the Russian's wouldn't believe you or decide to interpret your DDOS as an act of aggression performed on behest of your host nation and respond in kind, or even escalate up to and including the use of strategic thermonuclear weapons. While this may be an unlikely scenario the possible consequences are catastrophic, so is it ethical for you to risk the survival of global civilisation based on your need to be seen to do something? Probably not.