I have been on both sides of patent lawsuits in the past, but I am not a lawyer, so this is not legal advice.<p>You need a lawyer, but a lot of lawyers do this sort of thing pro bono for small companies. The EFF has a list of attorneys who can help. Interview at least 5 of them - ask for references, ask about past successes in this space, and ask about your case at a high level (give the one-minute overview of the case and ask about their plan).<p>The good news is that most software patents are invalid (thanks to the Alice decision* in 2014), and will be struck down in a process called inter partes review, which is a cheap way to challenge the validity of a patent through the USPTO. When you interview attorneys, you might want to ask prospective candidates about the validity of this patent and if they see this as a viable strategy.<p>Another dynamic at play here is that in many patent proceedings, the loser pays attorneys fees. You may not end up paying a dime, even without a pro-bono lawyer. Trolls like threatening lawsuits to pressure you into a settlement, but there's a lot at risk for them if they actually sue you for infringement.<p>*The full opinion on the Alice case is here, and is very interesting: <a href="https://www.supremecourt.gov/opinions/13pdf/13-298_7lh8.pdf" rel="nofollow">https://www.supremecourt.gov/opinions/13pdf/13-298_7lh8.pdf</a><p>EDIT: Also, if your lawyer suggests that you might be able to invalidate this patent, you may be able to band together with some of your competitors to share the cost of invalidating it.