The terrorism threat escalated in five countries during the course of 2005, according to Aon's new terrorism threat map.
The countries included Egypt, after attacks in Sharm al-Sheikh and the Red Sea resort of Dahab last week, and Denmark which has also seen rising threat levels.
Despite the London bombings last year, the terrorism threat rating remains unchanged at "elevated".
Paul Bassett, executive director of Aon's crisis management division, said of London: "It is not a case of 'if' but 'when' an attack will occur, and that threat remains."
Bassett said the nature of terrorist attacks was changing. "The war on terror has severely impacted the capabilities of large groups such as Al Qaeda to mount another 9/11-style attack. This has led to an increase in smaller groups who are more likely to go for softer targets."
He warned that the tactics needed a change in risk management strategies.