Oh, I see you helped yourselves to my Secure Chat logo - http://dribbble.com/shots/479881-Secure-Chat http://logopond.com/gallery/detail/165288 https://www.google.ca/search?q=secure+chat+logo - first page hit too Not cool at all, "cool guys around the world". -- (edit) Regardless of whether this was copied, over-inspired or independently conceived (but let's be realistic here), the generally accepted rule of the game…
Respectfully disagree. The generally accepted law is clear enough, as I understand it: that you have (automatic) copyright over your own design work, but not your idea. (Bad Analogy: I am free to make a for-profit game about flinging red birds at pigs, but I can't use Rovio's code or the Red Bird graphic) If you work as a graphic designer, you need to understand how this impacts on your work.
If you wish to protect your design any further, you need to specifically register a trademark to prevent confusion between businesses in the same industry.
It's clear that they haven't copied your design - the appearance of the work is quite different - and besides it seems plausible or even likely they came up with the (very nice) idea independently.
This is also important to understand for people hiring graphic designers for freelance work - in the UK at least, the designer maintains the copyright for commissioned work unless contractually agreed otherwise (even though the business can still trademark it). In theory, the designer can later prevent you from repurposing one of their designs. For example, if you later decide to start selling merch for your brand, you may have to renegotiate with the designer.
Edited to carefully note: IANAL, take this as advice at your own risk.
Further international edit, from wikipedia, emphasis mine: The United States, Canada and other countries also recognize common law trademark rights, which means action can be taken to protect an unregistered trademark if it is in use.