Just in case you haven't heard about this:
From Cryptoarticles
http://www.cryptoarticles.com/crypto-news/bitcointalk-user-spreading-malicious-clients-opal-considering-blockchain-rollback"We have received a report that concerns anybody who frequently visits the BitcoinTalk forums, and has updated one of their coin clients as of late. A user by the name of “diabanhxeo” has been spreading hacked cryptocurrency clients for various coins, containing a backdoor in order to steal wallet.dat files.
OPAL.png
The report was brought to our attention by the Opalcoin team, as they had noticed there was a hacked/misbehaving client on the network. It turns out one of the Bitcointalk forum users has been spreading an infected client; not just for OPAL, but also for different altcoins which have seen wallet updates as of late.
These hacked clients contain a backdoor, giving that user access to any computer where these malicious clients are installed. As a result, he/she will then breach your computer and attempt to steal any of your wallet.dat files. The wallet.dat file contains your coin balance and transaction history, so your coins could be gone before you know it.
Fake downloads are rather easy to spot though, as the download links are usually embedded in a reply, and not posted by the official coin developers or team members. It also appears this user targeting Windows users specifically, and uses RAR files to package the malicious client, whereas coin developers usually use ZIP files."
Edited for brevity...