Despite the advent of 'stealth' aircrafts jamming or ECM remain a valuable tool.
If anything, while 'stealth' can penetrate highly dense EM environment alone, an ECM assault on the defense will further confuse the defenders as to what he may face since both 'stealth' and 'non-stealth' aircrafts are equally lethal in terms of weapons.
Stand-off jamming is generally for blanket noise generation. The jammer aircraft usually does not specifically target any ground seeking radar but is concerned if there is an active EM environment, what kind is it, and its extent. The jammer aircraft usually remain just immediately outside of the weapons threat range.
Stand-in, aka 'escort' or 'penetration', jamming is much more dangerous and complex. The jammer aircraft accompanies the strike group and actually interpose itself between the seeking radar and the strike group to provide an EM shield. The jammer aircraft usually seek out as specific as possible the most threatening signals and sources and will target them. Stand-in jammers are usually 'quiet' until the very last moment in order to best exploit the electronic element of surprise against the seeking radars.
Both types can be performed by a single design. It is more a matter of mission type than of hardware. In other words, an EF-18 can be a stand-off jammer in one mission and a penetration jammer the next. However, the US is exploring making the B-52 into an ECM platform and with its size and subsonic speed, more likely this B-52 ECM variant will be confined to stand-off jamming missions. Not only can the B-52 can carry more ECM hardware but those hardware can be more powerful as well, enabling the B-52 to blanket the general area much more effectively.
When a defense is suddenly assaulted by an ECM attacker, the first thing the radar operator must do is to lower the gain in order to reduce the odds of having his hardware damaged. This is not about Hollywood where consoles explodes and sparks flying out of boxes. The damages are much more subtle. The analogy is having a sudden burst of light while looking through low-light enhancement devices, aka night vision goggles (NVG). The human eyes will require time to readjust. The radar is no different. But even though the electronics will recover quicker than the organic eyes, the few seconds is enough for the 'stealth' aircrafts to pass through an area they would rather either avoid or take extreme caution. The radar operator can also physically turn his antenna so that its main face is away from the highest intensity of the ECM assault to protect his hardware, but then again, the few seconds is all the 'stealth' aircrafts need at several hundreds km/h.
