ETA has survived largely due to the support of other terrorist organizations, and foreign supporters who are ignorant to the violence caused by the group, but sympathize with its message of self-determination. During the Basque exile of the Franco regime, a number of activists escaped into the mountains, where they began to establish bases for guerrilla warfare. ETA has modeled itself after other international terrorist groups, from which it has received support at times.

Basque supporter provide "safe houses," which are structures altered to include fake walls and floors and to conceal hiding places for escapees and kidnappings. According to the Risks International Report, ETA sent Jose Maria Arrumberri Esnaola to Argentina to study how to make such places. On his return he built 8 in Madrid alone.

ETA has contacts with other terrorist organizations even in the former Soviet Union an Libya. ETA has even been manipulated by groups like the Irish Republican Army and the Italian Brigades, who have no real interest in Basque nationalism but used them to destabilize Spain.

ETA sends members abroad for training in weapons, explosives and tactics; as early as 1964 they sen members to Cuba for training in kidnapping and sabotage, as well as to Algeria, Palestine, Libya, Lebanon, and South Yemen. The most popular site is Algeria, where it is estimated that hundreds of members have been sent for training. This training site is the part of the network with the Middle East, which was confirmed by the 1980 arrest in Amsterdam of four ETA members returning from paramilitary training with other members from Palestine.

The government is well aware of the international terrorist network, but there is only circumstantial evidence. The government has at times protested to the governments of Nicaragua, El Salvador, Argentina, and Uruguay, but it received little response until recently. In 1981 the Spanish government published a report of their findings about the international terrorist network. According to the report, ETA members received training in South Yemen, Lebanon, Czechoslovakia, Ireland, Uruguay, Cuba and Algeria; They received weapons and economic assistance from Czechoslovakia, the former USSR, Ireland, China, and Libya, and have conducted major business in Mexico and Cuba, which is now prohibited. ETA members have received refugee and asylum status mostly in France, even thought ETA is fighting for the independences of French Basque Country as well. Belgium and Venezuela are others country that have offered asylum to ETA members.

The terrorist organizations help support each other, including providing funding. The method used by ETA members is known as "knee capping" -a blackmail technique used to extort a "revolutionary tax" from local leaders. After so many deaths caused by ETA, local leaders and members of the upper class are well aware that ETA will live up to their threats is the extortion money is not paid. ETA also, has kidnapped many business men from the Basque Country as well as well known wealthy people like Julio Iglesias' father.