The United States maintains approximately 285 diplomatic facilities worldwide. Attacks on such facilities, and on U.S. diplomatic personnel, are not infrequent. U.S. Ambassador Christopher Stevens and three other U.S. personnel were killed in Benghazi, Libya on September 11, 2012, after armed individuals attacked and burned buildings on the main mission compound and subsequently attacked a second annex site where U.S. personnel had been evacuated. Five other U.S. Ambassadors have died by violent acts in the line of duty, although none since 1979. Since 1977, 66 American diplomatic personnel have been killed by terrorists. These events, along with recent attacks on U.S. embassies in Egypt, Sudan, Tunisia, Yemen, and Turkey, have drawn renewed attention to the challenges facing U.S. diplomats abroad, as well as to the difficulty in balancing concerns for their security against the outreach required of their mission. Under reciprocal treaty obligations, host nations are obligated to provide security for the diplomatic facilities of sending states. However, instances in which host nations have been unable or not fully committed to fulfilling this responsibility have sometimes left U.S. facilities vulnerable, especially in extraordinary circumstances. U.S. facilities therefore employ a layered approach to security including not only the measures taken by a host country, but also additional, U.S.-coordinated measures, to include armed Diplomatic Security agents, hardened facilities, U.S.-trained and/or contracted local security guards, and sometimes U.S. Marine Security Guard detachments. The inability to provide perfect security, especially against the evident threat of mob violence, has led some observers to question the deployment of personnel in high-threat environments. The Department of State's Assistant Secretary for Diplomatic Security, testifying in November 2009, underlined that "the Department currently operates diplomatic missions in locations where, in the past, we might have closed the post and evacuated all personnel when faced with similar threats." The rapid growth in the number of U.S. civilians deployed in the high-risk environments of Iraq, Afghanistan, and Pakistan spurred significant investment in recent years in the Department of State's capacity to provide security in dangerous areas through its Bureau of Diplomatic Security (DS). The challenges of providing security in these war-related areas may have also strained DS's capability to provide security for deployed diplomats in other hardship posts around the world. Observers have suggested that funding for embassy security follows a "boom and bust" cycle, in which major attacks are followed by a sudden influx of resources that may be difficult to expend in a well-planned manner. An influx of security-related resources in the 1980s, in response to the 1983/1984 bombings in Beirut, Lebanon, was followed by a lull in the 1990s when diplomatic security funding was greatly reduced prior to the 1998 attacks in Kenya and Tanzania. The subsequent State Department Accountability Review Board suggested that the preceding years of reduced spending for embassy security was a contributing factor to the vulnerability of the targeted embassies. This report provides background information on the authorities, regulations, and procedures in place at the Department of State regarding diplomatic security. It also describes several areas of potential congressional interest, including the Accountability Review Board process, whose conclusions the Secretary of State is required to report to Congress, and discussion of embassy security funding trends. It also examines the September 11, 2012, attack in Benghazi, Libya. The report may be updated to reflect ongoing developments. Under the 1963 Vienna Convention on Consular Relations and the 1961 Vienna Convention on Diplomatic Relations, nearly all countries around the world participate in reciprocal obligations regarding the diplomatic facilities of other countries in their territory. The United States is a state party to these conventions. Section 3 of Article 31 of the 1963 Vienna Convention on Consular Relations, "Inviolability of the consular premises," states that, other than in the case of fire or other disaster requiring prompt protective action, "the receiving State is under a special duty to take all appropriate steps to protect the consular premises against any intrusion or damage and to prevent any disturbance of the peace of the consular post or impairment of its dignity." Article 40 of the same Convention further states that "the receiving State shall treat consular officers with due respect and shall take all appropriate steps to prevent any attack on their person, freedom or dignity." An attack on an Ambassador is also covered under Article 29 of the 1961 Convention on Diplomatic Relations, which states "The person of a diplomatic agent shall be inviolable. He shall not be liable to any form of arrest or detention. The receiving State shall treat him with due respect and shall take all appropriate steps to prevent any attack on his person, freedom or dignity." The grounds of diplomatic missions are protected under the 1961 Vienna Convention on Diplomatic Relations. Article 22 (Section 1-3) of the Convention states: 1. The premises of the mission shall be inviolable. The agents of the receiving State may not enter them, except with the consent of the head of the mission. 2. The receiving State is under a special duty to take all appropriate steps to protect the premises of the mission against any intrusion or damage and to prevent any disturbance of the peace of the mission or impairment of its dignity. 3. The premises of the mission, their furnishings and other property thereon and the means of transport of the mission shall be immune from search, requisition, attachment or execution. The protection of U.S. government employees and facilities under Chief of Mission (COM) authority overseas from terrorist, criminal, or technical attack is the responsibility of the Secretary of State, as designated under the Omnibus Diplomatic Security and Antiterrorism Act of 1986, as amended. The act specifies that the Secretary of State must develop and implement (in consultation with the heads of other federal agencies having personnel or missions abroad where appropriate and within the scope of the resources made available) policies and programs, including funding levels and standards, to provide for the security of U.S. government operations of a diplomatic nature and foreign government operations of a diplomatic nature in the United States. Within the department, the Secretary has delegated these responsibilities to the Assistant Secretary for Diplomatic Security. The Assistant Secretary, who heads the Bureau for Diplomatic Security (DS), is responsible for, among other tasks: 1. Establishing and operating post security and protective functions abroad; 2. Emergency planning abroad; 3. Establishing and operating local guard services abroad; 4. Supervising the U.S. Marine Corps security guard program; 5. Liaising with U.S. private-sector security interests abroad; 6. Developing and coordinating counterterrorism planning, emergency action planning abroad, threat analysis programs, and liaison with other federal agencies to carry out these functions; 7. Developing and implementing technical and physical security programs, including security-related construction, radio, and personnel security communications, armored vehicles, computer and communications security, and research programs necessary to develop such measures. The mission of developing and implementing security policies and programs that provide for the protection of all U.S. government personnel (including accompanying dependents) on official duty abroad is executed through the DS, also established by the Omnibus Diplomatic Security and Antiterrorism Act of 1986, as amended. The DS provides protection to personnel, information, and facilities at over 273 embassies and consulates, and over 100 domestic Department of State locations. According to its website, "every diplomatic mission in the world operates under a security program designed and maintained by Diplomatic Security." The bureau is staffed by more than 34,000 employees worldwide—with roughly 90% of them contractors. Out of a total force of special agents of approximately 2,000, DS has nearly 800 special agents posted in regional security offices at over 250 posts worldwide. Its reach to diplomatic missions in 157 countries makes it the most widely represented American security and law enforcement organization around the world, according to its website. The Bureau of Diplomatic Security's workforce, excluding contractors, more than doubled between September 2000 and August 2012, as shown in Figure 1 . When serving abroad, DS special agents are referred to as regional security officers (RSOs). RSOs' responsibilities include not only managing security programs and formulating emergency contingency plans, but also providing the first line of defense for U.S. personnel and dependents, as well as facilities and sensitive information. RSOs are the primary advisor to the Chief of Mission (usually the Ambassador) on all security matters. In performing their functions, RSOs work closely with other groups including Marine Security Guards, surveillance detection teams, local guards, cleared American guards, local investigators, and host government officials. DS also provides Mobile Security Teams, dispatched from Washington, DC, to high-threat posts to conduct training for embassy personnel, their dependents, and local guards in protective tactics, as well as providing emergency security support, including protective security for COMs, surveillance detection operations, and assistance with post evacuations. DS also provides specially trained agents to lead contractor-provided personal protection teams and guard services in areas of ongoing conflict, where the host nation is unable or unwilling to provide the required level of security. In extreme situations, U.S. military assistance can be provided to the RSOs in the form of combat-equipped Fleet Anti-Terrorism Security Teams (FAST) provided by regional commanders. In an average year, DS receives over 1,000 threats and incidents against U.S. interests overseas. The security posture of each U.S. diplomatic facility varies based on the Department of State's assessment of local conditions. Regular reviews of threats to posts are conducted by the State Department. As part of this security review process, RSOs are required to inspect the physical security at each work facility every three years and to inspect potential properties before State Department acquisition.