Counter-Sniper Tactics, a brief description

The occurrence of sniper warfare has led to the evolution of many counter-sniper tactics in modern military strategies. These aim to reduce the damage caused by a sniper to a fighting force, which can often be harmful to both fighting capabilities and morale.

Once a sniper attack has occurred, the most difficult task is determining the sniper's location. Because snipers use camouflage, carefully choose their firing positions, and often attack from long distances, they are often able to strike and withdraw without ever being pinpointed. Being aware of the methods snipers use to conceal themselves is also integral to this, as most objects that are usually overlooked are able to function as a snipers' nest. This includes stationary cars that specifically have a hole cut out to allow the sniper a place to shoot out of, the driver functioning as the spotter. It could also include boxes or piles of rubble.
Counter-sniper tactics involves tactics used by a sniper against another sniper.

A friendly sniper is generally the most effective counter-sniper tool. With similar training, knowledge of the surroundings, and equipment, the friendly sniper can offer advice to the squad, enhanced searching capability, and a means to combat the enemy sniper directly. When told what to watch for, the squad can also act as additional eyes and ears for the friendly sniper. Aside from watching over the squad, the friendly sniper also has the option to detach and engage the enemy sniper. Without any outside help from the squad, the respective skills of each sniper play a significant role in determining victory. A sniper duel can frequently distract the enemy sniper from his mission.
Using Triangulation a technique at two or more locations can more accurately identify the position of a sniper at the time of firing.
The enemy's supersonic bullets produce a sonic boom, creating a "crack" sound as they pass by. If the enemy's bullet speed is known, his range can be estimated by measuring the delay between the bullet's passing and the sound of the rifle shot, then comparing it to a table of values. This is only effective at distances of up to 450 meters; beyond this, the delay continues to increase, but at a rate too small for humans to distinguish accurately. Also, in urban areas, the sound can give inaccurate results because the buildings in the area can relay false sound directions

If the sniper's general position can be determined by other means, the area can be bombarded by mortars or artillery. Rockets and even guided missiles are also usable, typically if the sniper has become a major problem and other neutralizing attempts have failed.
In urban settings or other environments with limited movement and fields of view, smoke can be an effective means to screen friendly movement. This can be used either to pass through and escape, or to close in on and eliminate the enemy sniper.
Ordinary soldiers can still do damage through smoke by firing randomly or on intuition, but a sniper loses his precision advantage and is far less likely to hit anything with his much lower possible shot volume. A determined enemy, such as an emplaced heavy machine gun, will fire randomly through smoke, so this is a dangerous tactic. It should also be noted that weapons of opportunity may also provide a smoke screen, anything from igniting a car's gas tank, oil drum, or using fragmentation grenades to throw up debris and quickly break line of sight and concentration. Flash-bang (distraction) grenades have a wider blast radius than fragmentation grenades.
If the squad is pinned down by sniper fire and taking casualties, the order may be given to rush the sniper's position. If the sniper is too far away for a direct rush, a "rush to cover" can also be used. The squad may take casualties, but with many moving targets and a slow-firing rifle, the losses are usually small compared to holding position and being slowly picked off.

If the sniper's position is known but direct retaliation is not possible, a pair of squads can move through concealment (preferably cover) and drive the sniper toward the group containing the targets. A pincer movement attack can be combined with artillery or mortar fire, so long as this is tightly coordinated, i.e. the target area covered by bombardment does not overlap with the movement of the counter-attacking troops. Even if bombardment does not kill or wound the sniper, it may flush him from cover.
While tradition methods of sniper detection have been proven to be effective, technology has progressed in the field of electronic countermeasures.

The 'sniper detector' system, named Boomerang, was developed through the Defense Advanced Research Projects Agency and can determine the bullet type, trajectory, and point of fire of unknown shooter locations. The system uses microphone sensors to detect both the muzzle blast and the sonic shock wave that emanate from a high-speed bullet. Sensors detect, classify, localize and display the results on a map immediately after the shot. The system sensors are usually mounted on a vehicle. The United States military is also funding a project known as RedOwl, which uses laser and acoustic sensors to determine the exact direction from which a sniper round has been fired. The RedOwl system has been tested on the PackBot robot from iRobot Corporation. While its reliable performance in urban environments with low buildings it might not be effective where the terrain is impossible for vehicles.

The U.S. Army is adjusting to the reality of hard-fought, guerrilla wars like the ones we're fighting in Iraq and Afghanistan, and redirecting its R and D towards a new breed of battlefield technology.
Consider a wearable set of electronics that detect a sniper's location. The unit weighs a mere 6.4 ounces, and is three inches square. It works by ignoring ambient noise and detecting the sound of gunfire. When that occurs, it alerts the wearer, then calculates the direction and distance of the source of the shots. The Soldier-Wearable Acoustic Targeting System (SWATS) can pinpoint the location of snipers after a single gunshot, audibly informing soldiers of the point of origin. A larger version of the technology can also be mounted on a moving vehicle, and it's capable of detecting shots even while moving at 50 mph. What's not clear yet is just how widespread the technology will be.
Alternatively a company from Alabama called Radiance has a new detection system called WeaponWatch, a fast-as-light infrared detection solution. It identifies weapons based on their unique muzzle bursts, and they claim that in 6 ms the device can detect a firing weapon from 1000 meters and still pin down the location of the attack to within 1.5 meters. This new system could eventually be integrated into an all-in-one system to not only find the perpetrator, but fire back at the target. Other technologies also include ballistic control in the form of smart bullets.
The XM25 rifle uses bullets that are programmed to explode when they have traveled a set distance, allowing enemies to be targeted no matter where they are hiding. The rifle also has a range of 2,300 feet making it possible to hit targets which are well out of the reach of conventional rifles.
The rifle's gun-sight uses a laser range-finder to determine the exact distance to the obstruction, after which the soldier can add or subtract up to 3 metres from that distance to enable the bullets to clear the barrier and explode above or beside the target. Soldiers will be able to use them to target snipers hidden in trenches rather than calling in air strikes. The 25-millimetre round contains a chip that receives a radio signal from the gun-sight as to the precise distance to the target. Todays technology finds ways to circumvent problems like targeting hidden snipers or using smart bullet technology. Electronic sniper countermeasures maybe the only effective system for quick detection. The changing face of war may be a harsh reality but thanks to technology it will filter down to civilian defense, hopefully to help the police one day...