A new code
On a certain level, it is unfortunate that the world of intelligence co-operation necessarily takes place in the shadows, for it can shed light on intriguing trends unfolding across the region.
Anecdotal evidence, for example, suggests South Korea and Japan are increasingly co-operating, particularly about China.
Historical suspicions mean the two have hardly been soul mates and such exchanges are unlikely to be formalised any time soon.
Just last week, a plan to formally codify military and intelligence exchanges this month was put on ice amid election-year sensitivities in Seoul.
But a range of insiders on both sides describe a flourishing relationship nonetheless.
'The stealthy nature of intelligence work is perfect for driving co-operation that would otherwise die in the light,' said one well-connected South Korean official. 'Ship visits and joint exercises might raise political temperatures in both countries, but you don't have those worries with intelligence sharing - so long as it is kept informal.'
They may be economic competitors who have routinely spied on each other, but other issues are pushing them together. Reliant on oil imports, both have a thirst for analysis on tensions in the Strait of Hormuz beyond what they get second-hand from Washington.
And, more sensitively, they are both examining a rising China, from its military capabilities and strategic intentions to fears about the impact of any prolonged period of political instability in Beijing.
This last point is highly sensitive yet something that taxes strategic planners in countries that are finding themselves ever more engaged with China's economy and diplomacy.
As one insider explained: 'In plain terms, it is not just a question of finding out what China can do, but assessing where it might be heading, and what would happen if things go wrong. That's the real sexy stuff.'
North Korea is another issue where there is considerable room for intensified co-operation as the two both try to improve their intelligence operations.
So if things are humming along, what are the precise limits? Sheryn Lee, a researcher at the Strategic and Defence Studies Centre of the Australian National University, said she believed that while informal intelligence sharing between South Korea and Japan may have increased, a more formal arrangement was hard to imagine given mutual suspicions. 'There has been an increased frequency and volume of exchanges, examining issues such as China's movements and capabilities - something like whether the launch of the aircraft carrier Varyag represented a threat would be an example of the sort of thing they might swap notes on,' she said.
'But there is not yet the depth. As for the real nitty-gritty - sharing details of their signals and human intelligence capabilities and setting priorities, for example - that is just not going to happen. That sort of thing really needs a formal agreement.'
She added: 'And it should be remembered that these countries have a long history of spying on each other, so there is always going to be mistrust in the background, whatever strategic interests they share.'
Greg Torode is the Post's chief Asia correspondent. email@example.com