Democratic People's Republic of Korea
SWIFT cuts North Korean banks (March 17, 2017)
Financial communications platform SWIFT has dropped the remaining North Korean banks from its system amid growing political pressure
On March 16, (2017) financial communications platform SWIFT announced it would disconnect the last four remaining North Korean banks on its system. The decision was taken after Belgian regulators threatened to prevent the platform from offering its services to UN-sanctioned banks. SWIFT stated the move was made as the banks were “no longer compliant with SWIFT’s membership criteria”. However, it is widely thought broader political pressure prompted the decision.
All North Korean banks cut by the platform are currently under sanction by the US Treasury. One, the state-owned Foreign Trade Bank of the Democratic People’s Republic of Korea, was sanctioned by the US in 2013 for funding nuclear proliferation.
SWIFT’s decision to disconnect the North Korea’s remaining banks means the state no longer has access to a major means of circumventing financial sanctions.
Cuba was also previously banned, according to DW:
Based in Belgium, SWIFT claims political neutrality, but has bowed to US influence in the past, blocking transactions to Cuba and Iran.
I'm not sure of the details, from when to when, that ban applied to Cuba.
Looking through the Wikipedia article on SWIFT, I could find no formal ban on Cuba, but...
U.S. control over transactions within the EU
On 26 February 2012 the Danish newspaper Berlingske reported that US authorities have sufficient control over SWIFT to seize money being transferred between two European Union (EU) countries (Denmark and Germany), since they succeeded in seizing around $26,000 that was being transferred from a Danish businessman to a German bank. The transaction was automatically routed through the US, possibly because of the USD currency used in the transaction, which is how the United States was able to seize the funds. The money was a payment for a batch of Cuban cigars previously imported to Germany by a German supplier. As justification for the seizure, the U.S. Treasury stated that the Danish businessman had violated the United States embargo against Cuba.
So, it appears that at least some USD transaction relating to Cuba were affected.
On the other hand, the Wikipedia article on SWIFT doesn't mention North Korea at all, so it's probably rather incomplete, despite its length.
SWIFT itself, on its sanctions-related page, makes no mention of North Korea (or Cuba), as such. They have rather complex verbiage that covers their assess and only recognize a (past) formal ban on Iran:
In March 2012, pursuant to international and multilateral action to intensify financial sanctions against Iran, SWIFT was exceptionally prohibited under EU Regulation 267/2012 from providing financial messaging services to EU-sanctioned Iranian banks. SWIFT is incorporated under Belgian law and had to comply with this regulation as confirmed by its home country government. SWIFT implemented the regulatory obligation by disconnecting the related EU-sanctioned Iranian banks. In January 2016 many of the affected banks were de-listed by the EU, and were subsequently reconnected to SWIFT. [...]
In exceptional circumstances, and where the interest of the stability and integrity of the wider global financial system are at risk, SWIFT may also need to restrict customers’ access to the network. In an isolated event in November 2018 SWIFT thus suspended certain Iranian banks’ access to the messaging system. This step, while regrettable, was taken in the interest of the stability and integrity of the wider global financial system, and based on an assessment of the economic situation.
The key issue is that they disclaim responsibility for actual transactions:
SWIFT does not monitor or control the messages that users send through its system. All decisions on the legitimacy of financial transactions under applicable regulations, such as sanctions regulations, rest with the financial institutions handling them, and their competent international and national authorities. As far as financial sanctions are concerned, the focus of SWIFT is to help its users in meeting their responsibilities to comply with national and international regulations.
On the other hand, if you look at SWIFT's software manual they have features that automatically raise flags for "Cuba". And they make a point that they only raise this flag appropriately, e.g.:
In the MT example, it’s highly likely the payment would be one of the 10% typically stopped by a sanctions filter, triggering an investigation. This is because the word ‘Cuba’ appears in the name and address and it’s otherwise unclear where the payment is going.
In the ISO 20022 example the postal address (PstlAdr) unambiguously identifies the country that the Cuba Sports Bar & Grille is based in - the United States – using a standard 2-character country code (US). It’s also clear that ‘Cuba’ is part of the name (Nm) of the establishment, so no ‘false positive’ compliance hit should occur. The payment can therefore be processed smoothly with the money arriving on time and the bank benefitting from the reduced cost of manual processing.
So reality vs formal ban...