President Barack Obama has considerably expanded the use of three lethal weapons in the war against terrorism that will likely return to bite the hand currently feeding them.

Today’s well-deserved killing of Abu Yahya al-Libi, al Qaeda’s number two, is an example of one of those weapons. Ayman Al-Zawahiri may be the next target as successor to Osama bin Laden, who was killed by Navy Seals in Pakistan in May 2011.

The weapon in this case is Obama’s decision to authorize an international assassination campaign against America’s enemies beyond judicial or independent oversight. Even an American citizen, Anwar al-Awlaki, was killed as part of this campaign. Each attack usually kills or wounds others nearby and the collateral damage is said to be unavoidable.

Over time, this systematic campaign of assassinations is likely to generate enough rage among admirers of those killed to rationalize more ferocious terrorism against US civilians. The terrorists cannot reach US generals and top leaders, who they see as enemies, so they may feel justified in taking the lives of other Americans whenever they can. The admirers are not numerous but it takes just a couple of terrorists to cause havoc.

Al-Libi’s death may have cut off a venomous head of the snake but al Qaeda is no longer a centrally commanded body of fanatics. It is heavily splintered into small local groups, including free lancers inspired by its message but outside its control.

However legal and justified international assassination might look to many Americans and Obama, the enemies at the receiving end will not easily forget their humiliation. The people killed belong to tribal cultures, where clans and families nurture grudges and seek revenge from generation to generation. They too will seek technologies to obtain vengeance within the US homeland. It is just a matter of time. They live in local communities where failure to take revenge especially against outsiders is seen as dishonor for the entire clan.

The US homeland has been safe for over a decade. But that does not mean the enemies of America and its allies have disbanded or disintegrated. Unless the US reduces use of Obama’s three lethal weapons, those enemies will lick their wounds and return with more hate-filled deviousness and deadlier means. However medieval, this is a part of their way of life. It has little to do with religion and much more to do with the traditions of their local communities.

The second lethal weapon is the much increased use of drones equipped with ever better arms and means of espionage. Drone attacks have burgeoned under Obama, killing over 2400 people up from about 430 before he took over, according to New America Foundation estimates. Currently, the US has a near monopoly over the use of drones but others are working hard to catch up, just like some did over nuclear weapons.

It is very unlikely that anyone could conduct drone attacks on the US homeland, given the vast oceans on both sides. But that is an added incentive to hurt America’s allies who are not so well protected by nature. It is also an incentive to conduct suicide and other bomb attacks on the homeland. US security is not easy to penetrate for terrorists but the more often drones are used to lethal effect, the more those at the receiving end will strive to slip through the cracks.

These are not formal wars where one side gets defeated and settles into a peace imposed by the victor. However justified hurting its enemies might be in the eyes of the US, it cannot rule out that the families, children and friends of those enemies will rise to fight another day if strikes on them continue without relent. Some anti-terrorism experts are already saying that the next generation’s fanatical ideological positions are more virulent than those of the persons currently being killed by Obama’s campaign and the drone attacks.

The third lethal category is cyber weapons. Obama is reported to have authorized its use against Iran and other unnamed countries. The US may have the technological lead currently in both offensive cyber weapons and defenses against them, but the knowledge needed to build them is already proliferating.

These are fluid weapons and their acquisition by enemies is almost impossible to control. A country like Iran may be coerced and threatened out of building nuclear weapons. Perhaps, its nuclear facilities can be safely bombed without causing nuclear fallout.

But cyber weapon laboratories are undetectable. They are not clumped together in hidden locations. Nor are there international agencies to police them. They do not distinguish between military uniforms and civilian apparel.

Of all countries, the US is the most heavily computerized. There can be no certitude that its electricity, banking or defense networks cannot be hacked or infected. Such experimental attacks have already been reported.

It will be very difficult to prevent those unable to wreak vengeance on the US through drone attacks from using cyber-attacks instead. People may not be killed or wounded as by a suicidal terrorist but the cost in disruption and fear will be higher. A wide cyber-attack on banks and stock markets could halt the modern economy and make trillions unrecoverable in the savings of ordinary people.