Cyberspace may still seem an abstraction to some, but it underpins much of daily life - from families keeping in touch via e-mail, to airplanes staying on course through computerized traffic control, to maintaining power grids, to shopping on the Internet.
In the rush to defend against terrorism, the federal government rightly has put "cyber-security" high on its list of priorities. President Bush recently appointed a special adviser on the subject, Richard Clarke, who will be an integral part of the homeland defense effort.
Mr. Clarke, who's been working in this field for years, will have plenty to do. From the proliferation of destructive computer viruses in recent years to reports that the Sept. 11 hijackers used e-mail and encrypted messages, evidence abounds that cyberspace is all too open to nefarious doings.
A major part of the problem is the vulnerability of most computer systems in commercial and government use to sabotage. The security holes and unlocked "backdoors" in systems can easily be exploited. The main result, so far, has been mischiefmaking, such as defacing websites. But the possibility exists of far more harmful intrusions by committed terrorists.
Last year, a Pakistani hacker cracked the computers of the American-Israel Public Affairs Committee, leaving anti-Israel messages and stealing credit-card numbers and e-mail addresses. Four years ago, a Swedish hacker broke into the 911 emergency phone system in central Florida, causing it to shut down temporarily. Government and military secrets have been snatched from computers.
Among Clarke's first tasks will be closing security weaknesses in federal computers - weaknesses already documented by the General Accounting Office. That job alone covers a vast amount of ground, such as the huge, vital systems operated by the Social Security Administration and the Internal Revenue Service.
But homeland defense of cyberspace also will require close looks at state and local systems that coordinate emergency services such as fire and police. Utility power grids have to be protected. Companies that rely on networked computers to conduct business must be encouraged to create backup systems.
Not least, Clarke will have to enlist computer makers and software designers who can do more to build in better security - for the sake of good business and good citizenship.