Additional details have emerged on the Jan. 24 explosion at Domodedovo International Airport in Moscow that killed 35 people and injured as many as 131. The Domodedovo airport has faced previous attacks by militants, and in response has instituted stronger security measures intended to keep would-be attackers from bringing explosive devices onto planes. However, this bombing appears to have targeted an area with a high amount of foot traffic near the entrance to the airport, which has far less security than boarding areas near the planes themselves. Officers on the scene estimated the explosion to be equivalent to one caused by 5 to 10 kilograms (about 11 to 22 pounds) of TNT. Based on these estimates, the explosive, which may have been packed with shrapnel to increase its lethality, easily could have been contained in a typical bag or a suicide vest that would be difficult to spot. This is especially true if the device was concealed under a large jacket, such as one required for Moscow's winters. Indeed, some reports have indicated the device was a suicide belt hidden under the attacker's clothing. More information has also emerged on the profile of the perpetrator. Multiple official reports have confirmed that a single suicide bomber carried out the attack. Russian law enforcement sources told STRATFOR that security camera footage of the bomber indicates that he or she is of Chechen or Dagestani ethnic descent. Media reports say officers on the scene found the head of a man in his 30s believed to be the bomber and described as "Arab" in appearance. This term may actually refer to a person from the North Caucasus, the residents of which sometimes are characterized as Arabs in Russia, rather than to an Arab militant from outside Russia's borders. RIA Novosti and other Russian media outlets have reported that prior to the attack, Russian security services were on high alert, looking for three individuals from the North Caucasus believed to be planning an attack on a Moscow airport. Interfax reported that the attack may be linked to a Dec. 31 explosion at a sports club in southeastern Moscow. The earlier explosion killed one woman, who was believed to be preparing an improvised explosive device for a suicide attack. This led investigators to seek out the three aforementioned suspects. According to Interfax's law enforcement source, these three suspects brought the attacker to Domodedovo airport, and one of them or a fourth individual — the report says the attacker was a woman — was responsible for setting off the explosive. Suspicion will thus focus on the Caucasus Emirate, and Russian security services are already searching for the attacker's handlers. While these reports are not yet confirmed, it is clear that the attackers chose a low-security yet high-profile target for their attack: the public area where passengers check in and where families and drivers wait for arrivals. This is a particularly difficult area for security services to monitor. Since this attack, like the March 2010 attack on the Moscow Metro, focused on a soft target, it indicates the limited capability of the attackers, whether they are militants from the Caucasus or elsewhere. While these attacks can cause large numbers of casualties — as this one did — the attackers apparently remain unable to breach security measures or attack Russia's most important facilities and individuals. Domodedovo International Airport has been targeted by Caucasian militants in the past, notably in a 2004 dual airplane attack. Since then, security has been increased at Russian airports, making it more difficult to smuggle an explosive device past check-in. However, the militants responsible for this attack appear to have adapted their approach to target the part of airports most accessible to the public. These areas are consequently among the busiest and the most dangerous in air travel, since people have any number of reasons to be waiting there and are often not screened until they attempt to enter through security.