Henry Farrell in The Washington Post's Monkey Cage explains Russia is hinting at a new Cold War over SWIFT. So what’s SWIFT?. I didn't know of any of this.
"Because SWIFT plays such a crucial role in international financial transactions. Russia’s own financial system relies on SWIFT and would likely be crippled if it were no longer able to use the system. Russian banks would have great difficulty in engaging in transactions with each other."