The ruble rumble is a mixed blessing for U.S. banks.

It has awoken markets that spent much of the year in a deep sleep. The Deutsche Bank FX volatility index is at its highest levels for the year, for example, as is the Chicago Board Options Exchange’s measure of crude-oil volatility. And while the CBOE’s index of bond-market volatility hasn’t returned to its October high, it has been rising for a week and is at its second-highest level in 2014
Rising volatility generates trading volume, producing revenue for fixed-income, currency and commodity trading desks. It also can generate income for derivatives units, as investors hedge positions.

Of course, volatility isn’t without its risks. Even though banks now hold less trading inventory than they did in past eras, traders can get caught on the wrong side of a market move. That is what appeared to have happened recently at Jefferies. It disclosed Tuesday that fixed-income revenue for its fiscal fourth quarter had declined 73%, in part because of a selloff following a late September legal ruling involving Fannie Mae and Freddie Mac.

There is also some risk of losses at banks stemming directly from Russia. Citigroup, the U.S. bank with the highest direct exposure, says it has hedged substantially all of its $1.6 billion of net investment there. But it also has $7.4 billion of assets such as corporate and consumer loans and local government debt in Russia. And if the Russian crisis becomes contagious, investments in other emerging markets could also suffer.

The flattening of the yield curve, as investors flee to the safety of U.S. Treasurys, may put pressure on bank earnings, as well, by squeezing net interest margins. But this is likely to be offset by the rising value of bonds held by banks thanks to falling long-term interest rates.

For now, banks look like they could come out of this fight without too many bruises.