Office of Foreign Assets Control has been highly effective. It has blocked $2.3 Billion worth of cash and property in the US, much of it Iranian.
OFAC published its annual Terrorist Assets Report for 2014 and there are some interesting things in there. For example, it lists the top eight terrorists funds that were blocked. Al-Qaida is at the top. Because this report focuses on sanctions on terrorism and not other types of sanctions, Russia is not at the top.
About the Author: Marcus Maltempo is a compliance professional with more than a decade of experience helping banks, law firms and clients manage investigations and regulatory responses. He is the author of the forthcoming book History of Money Laundering: How criminals got paid and got away.