In recent weeks, major American banks, from Bank of America (BAC 1.11%) to JPMorgan Chase (JPM 1.06%) have suffered a series of distributed denial of service (DDoS) attacks. Reportedly sponsored by elements within the Iranian government, the attacks are said to be both "significant" and "ongoing." Worse than that -- they may be spreading.

Citing "unusual" traffic issues on its website, Ally Financial bank -- the old auto financing arm of General Motors (GM -0.04%) -- raised concerns this morning that the DDoS attacks, which affected larger American banks earlier in the month, may be reaching farther down in the banking infrastructure. Potentially, as far as small banks with less robust IT departments than you'd expect to find at B of A and JPM. IT departments that could potentially be more vulnerable to attack.

Dismissing concerns, Ally denied that it has "experienced the type of disruption that has been associated with the [DDoS] attacks" at other banks. But when pressed for details on exactly what "unusual" traffic it was seeing, Ally's spokeswoman declined to comment.