Win32/Trojan.Ransom.4ca is a heuristic detection for several anti-virus solutions. If your anti-virus detected the Win32/Trojan.Ransom.4ca virus it is possible your computer is infected with more malware. Malware is a umbrella term that refers to any software program deliberately created to perform an un-authorized and often harmful action.
Since the Win32/Trojan.Ransom.4ca is a general detection it is possible you picked it up at a compromised (hacked) website or by downloading a malicious file. Nevertheless you need to check your computer, it is possible there is malware left that is not detected. Malware programmers tent to use a dozen of methods to prevent detection by any antivirus solution.