Luckily, the common perception that Hawala financing is paperless is wrong. The transfer of information regarding the funds often leaves digital (though heavily encrypted) trails. Couriers and "contract memorizers", gold dealers, commodity merchants, transporters, and moneylenders can be apprehended and interrogated. Written, physical, letters are still the favourite mode of communication among small and medium Hawaladars, who also invariably resort to extremely detailed single entry bookkeeping. And the sudden appearance and disappearance of funds in bank accounts still have to be explained. Moreover, the sheer scale of the amounts involved entails the collaboration of off shore banks and more established financial institutions in the West. Such flows of funds affect the local money markets in Asia and are instantaneously reflected in interest rates charged to frequent borrowers, such as wholesalers. Spending and consumption patterns change discernibly after such influxes. Most of the money ends up in prime world banks behind flimsy business facades. Hackers in Germany claimed (without providing proof) to have infiltrated Hawala-related bank accounts. The problem is that banks and financial institutions - and not only in dodgy offshore havens ("black holes" in the lingo) - clam up and refuse to divulge information about their clients. Banking is largely a matter of fragile trust between bank and customer and tight secrecy. Bankers are reluctant to undermine either. Banks use mainframe computers which can rarely be hacked through cyberspace and can be compromised only physically in close co- operation with insiders. The shadier the bank - the more formidable its digital defenses. The use of numbered accounts (outlawed in Austria, for instance, only recently) and pseudonyms (still possible in Lichtenstein) complicates matters. Bin Laden's accounts are unlikely to bear his name. He has collaborators. Hawala networks are often used to launder money, or to evade taxes. Even when employed for legitimate purposes, to diversify the risk involved in the transfer of large sums, Hawaladars apply techniques borrowed from money laundering. Deposits are fragmented and wired to hundreds of banks the world over ("starburst"). Sometimes, the money ends up in the account of origin ("boomerang"). Hence the focus on payment clearing and settlement systems. Most countries have only one such system, the repository of data regarding all banking (and most non- banking) transactions in the country. Yet, even this is a partial solution. Most national systems maintain records for 6-12 months, private settlement and clearing systems for even less.