Systems that process private data, such as those at the Social Security Administration or IRS, are typically big, with multiple processors all backed up to safeguard against failure. We don't worry too much about them. But maybe we should. Transaction data doesn't go into and out of big systems the way it used to, via punch cards or magnetic tape. Transactions are now routinely collected remotely and transmitted to and among big systems through networks.
Network traffic is controlled by network servers.
Therefore, merely backing up mainframes is no longer adequate to ensure trust in large systems. A new point of vulnerability, the network server, has crept into large systems. Agency managers can have confidence that mainframe data is safe, but they would be mistaken to assume transactions are getting to and from the mainframes safely. Network transactions bring dangers of contamination from viruses, normal small-system failures, sabotage and natural disasters. Server security is not a sexy subject.