Foxiest of the Hounds

Foxiest of the Hounds is an achievement/trophy in Deus Ex: Human Revolution. It is earned by completing the game without setting off any alarms. It is similar to the in-game, per-mission bonus "Smooth Operator", which awards 250 XP.

This does NOT mean that you can never get an "Alerted" status from enemies, or even "Hostile" with open combat. It simply means that no alarms can be tripped, such as from a camera spotting you or a body, an alerted enemy touching an un-hacked alarm panel, etc.

The exceptions to this are the alarms that sound at the end of the Tai Yung Medical and Singapore missions.

Strategies

 * In general, either speed or stealth is needed; alarms are never instantaneous and you will always have a chance to prevent it, be it from a camera becoming suspicious (yellow light) or an enemy making a B-line for an alarm panel. The only exception to this is destroying a camera outright, which will immediately set off an alarm.
 * If unhacked alarm panels are nearby, never use weapons that aren't silenced unless you have the means to quickly gun down everyone showing up on your radar, including civilians (who will possibly run off and alert distant enemies). Non-lethal takedowns are the only 100% silent way to remove an enemy, and even silenced weapons generate enough noise to be heard at point-blank range. This rule also applies to the stungun, though this could be a bug. (confirmed on PC)
 * Remember that the stungun can temporarily disable cameras and other security devices without causing an alarm. This can be useful to give you extra time to move a body; or, if a camera sees you and you have no time to get into cover, and no energy for the cloak, for a last ditch attempt you can rush the camera and quickly "stun" it, giving you time to get away.
 * Don't forget that you can "throw" bodies great distances, it is possible to cloak and throw a body out of a camera's view, even upon becoming suspicious, before it sets off an alarm; but you must be quick, see above.
 * It is wise to upgrade your capture software to enable you to shutdown turrets and bots; while getting their attention does not cause an alarm directly, the gunfire will get anyone's attention in the room.
 * Obviously, having an upgraded cloak can make cameras and bots trivial, but do not forget to move bodies quickly.
 * The cloak allows you to move through security lasers freely. In lieu of this, you may drag a guard near the lasers and they will shutdown as long as the body is in proximity.
 * There is no reason not to hack and disable most alarm panels, however if you cannot do this safely, consider placing gas mines near them (using the cloak if need be). Be careful not to set off your own traps.
 * Enemies who spot bodies will often set off alarms; in most cases however they will investigate the body first, giving you a chance to neutralize them or move into a strategic location.
 * If you perform a takedown while cloaked, you will uncloak for the animation but since the game essentially pauses during this time, you will not be spotted by enemies or bots/cameras. As soon as the animation is over you are recloaked, and you will not be seen even if you are in direct line-of-sight. This can be useful for quickly dealing with an enemy that's about to trip an alarm.

Trivia
This achievement/trophy is a reference to the Metal Gear Solid game series. The main character, Solid Snake, was a member of a black ops group, "High-Tech Special Forces Unit FOXHOUND". Also, the visual representation for the achievement/trophy is a masked guard with exclamation points above his head, a common sight in all Metal Gear games.