基于免疫和代码重定位的计算机病毒特征码提取与检测方法

针对当前感染率高、威胁性极大的感染型计算机病毒,提出了一种基于免疫和代码重定位的计算机病毒特征码提取与检测方法.借鉴生物免疫系统机理,定义了计算机系统中的自体、非自体、抗体、病毒检测器、病毒基因等免疫概念,利用感染型病毒独特的代码重定位特性来提取病毒基因、构建病毒基因库,并在此基础上建立了自体/非自体、病毒基因库和病毒检测器动态演化模型.理论分析与实验结果表明,本方法有效克服了传统方法存在的自体集完备性问题和病毒检测器抗体完整性问题,因而比传统方法有更好的效率与适应性.      

基于代码图像增强的恶意代码检测方法

网络空间面临的恶意代码威胁日益严峻,传统恶意代码检测方法在恶意代码攻防对抗中逐渐暴露弊端。针对此现状,该文提出了基于代码灰度化图像增强的恶意代码检测方法,使用恶意代码ASCII字符信息和PE结构信息对传统恶意代码灰度化图像方法进行改进,构建RGB三维图像作为原始数据输入到检测算法,并使用一种带有空间金字塔池化结构的VGG16神经网络模型对恶意代码图像进行训练和预测。该文还提出了一种基于多标注归一化表示的方法来提高样本标签的可靠性,实验结果表明:该方案可以有效应对加壳、混淆等对抗手段,对新型恶意代码具有良好的检测效果。     

路径条件驱动的混淆恶意代码检测

代码混淆是恶意代码隐藏自身的主要手段之一.本文提出了一种新的动态检测方法,能够有效检测混淆后的恶意代码.该方法能够利用ISR进行动态调试.在调试过程中通过对路径条件的约束求解,驱动恶意代码执行不同的路径更深入地检测隐藏恶意代码.此外,对于需要读取外部资源的恶意代码,恶意行为往往需要结合外部资源才能检测.本文方法能够准确定位外部资源并结合原始恶意代码进行检测,提高检测的准确性.在原型系统的测试中,与12种杀毒软件的横向测试表明,该方法在对混淆恶意代码检测中能有效地降低漏报率.     

多策略网页恶意代码检测算法的实现

随着互联网的迅速发展,人们在浏览网页的时候容易受到网页恶意代码的攻击.针对这些问题,提出了一种基于多策略的网页恶意代码检测方法.对恶意网页代码特征进行分析,通过运用词频统计的方法对网页代码进行特征挖掘,获取关键特征值后,分别利用支持向量机算法、朴素贝叶斯算法、神经网络算法和多策略的算法建立分类模型,设计实验对4种分类模...     

基于IRP的未知恶意代码检测方法

目前采用的基于API的恶意代码检测方法只能检测运行在用户态的恶意代码,不能检测运行在内核态、采用内核API调用的恶意代码.为此,文中提出基于I/O请求包(IRP)的未知恶意代码检测方法.应用朴素贝叶斯、贝叶斯网络、支持向量机、C4.5决策树、Boosting、否定选择算法及针对IRP序列特点改进的人工免疫算法对捕获的I...     

基于遥感的合肥市建成区时空变化分析

通过对恶意代码行为和特征提取技术的分析,提出了基于虚拟环境下实现恶意代码检测的方法,设计了相应的检测系统;利用虚拟化技术,通过Docker容器简化检测环境的配置,增强了代码检测的隔离性、安全性;并建立相应的实验平台开展测试,为检测恶意的网络行为提供了支持。     

Android系统中恶意代码的动态检测技术研究

随着手机普及程度的日益提高,人们对智能手机的依赖性加重,手机的安全性问题变得愈加突出.根据Android安装包(APK)文件的权限调用和Android系统的应用程序接口(API)函数调用情况,设计了一种基于API拦截技术的检测恶意代码的动态检测方法.实验结果表明,该方法可以有效检测并报告Android系统中的恶意代码.     

抗人前列腺素D合成酶嵌合抗体基因的构建

采用RT-PCR技术,从1株稳定分泌抗人L-PGDS单克隆抗体的鼠杂交瘤细胞中扩增抗体的可变区基因,得2个Vk和1个VH．序列经Igblast比对分析,其中1个VK为鼠骨髓瘤细胞系内固有的无功能基因;另-Vk和VH具备鼠抗体可变区特征,为抗体功能基因．经双酶切,将抗体可变区功能基因分别与表达载体pAG4622、pAH4604中的人IgG相应恒定区相连,构建成抗人L-PGDS的人-鼠嵌合抗体基因。     

缓冲区溢出攻击的动态检测与防范

缓冲区溢出是被黑客利用得最多的漏洞之一,为了对其进行动态的检测及防范,提出了一种基于地址认证的缓冲区防护(Authentication-Guard)技术.该技术通过修改编译代码,动态检测缓冲区是否发生溢出,对返回地址进行保护,避免了恶意代码的运行.利用该技术,攻击者无法利用计算缓冲区长度来绕开检测,同时也避免了返回地址不可预知的问题.     

Igh-V or closely linked gene(s) control immunological memory to a thymus-independent antigen

Mice mount a normal primary antibody response on stimulation with the thymic-independent antigen trinitrophenylated lipopolysaccharide (TNP-LPS). Although we have previously reported the generation of functional B-memory lymphocytes to TNP-LPS, this memory response was only observed in few mouse strains. Here we have used congeneic mouse strains in an attempt to locate the genetic regions involved in the memory response. We show that genes of the major histocompatibility complex (MHC) do not have a critical role but that genes coding for the variable region of immunoglobulin heavy chains or gene(s) closely linked to them are required for memory cell induction by TNP-LPS.     

Organization and sequences of the variable, joining and constant region genes of the human T-cell receptor alpha-chain

An essential property of the immune system is its ability to generate great diversity in antibody and T-cell immune responses. The genetic and molecular mechanisms responsible for the generation of antibody diversity have been investigated during the past several years. The gene for the variable (V) region, which determines antigen specificity, is assembled when one member of each of the dispersed clusters of V gene segments, diversity (D) elements (for heavy chains only) and joining (J) segments are fused by DNA rearrangement. The cloning of the beta-chain of the T-cell antigen receptor revealed that the organization of the beta-chain locus, which is similar to that of immunoglobulin genes, is also composed of noncontiguous segments of V, D, J and constant (C) region genes. The structure of the alpha-chain seems to consist of a V and a C domain connected by a J segment. We report here that the human T-cell receptor alpha-chain gene consists of a number of noncontiguous V and J gene segments and a C region gene. The V region gene segment is interrupted by a single intron, whereas the C region contains four exons. The J segments, situated 5' of the C region gene, are dispersed over a distance of at least 35 kilobases (kb). Signal sequences, which are presumably involved in DNA recombination, are found next to the V and J gene segments.     

The chicken B locus is a minimal essential major histocompatibility complex.

Here we report the sequence of the region that determines rapid allograft rejection in chickens, the chicken major histocompatibility complex (MHC). This 92-kilobase region of the B locus contains only 19 genes, making the chicken MHC roughly 20-fold smaller than the human MHC. Virtually all the genes have counterparts in the human MHC, defining a minimal essential set of MHC genes conserved over 200 million years of divergence between birds and mammals. They are organized differently, with the class III region genes located outside the class II and class I region genes. The absence of proteasome genes is unexpected and might explain unusual peptide-binding specificities of chicken class I molecules. The presence of putative natural killer receptor gene(s) is unprecedented and might explain the importance of the B locus in the response to the herpes virus responsible for Marek's diseases. The small size and simplicity of the chicken MHC allows co-evolution of genes as haplotypes over considerable periods of time, and makes it possible to study the striking MHC-determined pathogen-specific disease resistance at the molecular level.     

Major reorganization of immunoglobulin VH segmental elements during vertebrate evolution

In mammals, the immunoglobulin heavy-chain variable region (VH) locus is organized in a linear fashion; individual VH, diversity (DH), joining (JH) and constant (CH) region segments are linked in separate regions. During somatic development, coding segments flanked by characteristic short recombination signal sequences, separated by intervening sequence regions that may exceed 2,000 kilobases (kb), are recombined. Combinatorial joining of different segments as well as imprecision in this process contribute to the diversity of the primary antibody response; subsequent mutation further alters functionally rearranged genes. This basic somatic reorganization mechanism is shared by six major families of genes encoding antigen receptors. Previously, we have shown that multiple germline genes and mammalian-like recombination signal sequences are associated with the VH gene family of Heterodontus francisci (horned shark), a primitive elasmobranch. Studies presented here demonstrate that segmental reorganization involving mammalian-like DH and JH segments occurs in the lymphoid tissues of this species. In marked contrast to the mammalian system, we find multiple instances of close linkage (approximately 10 kb) between individual VH, DH, JH, and CH segments. This unique organization may limit combinatorial joining and be a factor in the restricted antibody response of this lower vertebrate.     

Functional and molecular organisation of an antigen-specific suppressor factor from a T-cell hybridoma

Thymus-dependent (T) lymphocytes have been shown to have antigen specificity. The antigen receptor on T lymphocytes, in contrast to that on B lymphocytes, does not appear to be of the conventional immunoglobulin (Ig) type. Studies on the antigen-specific factors derived from helper and suppressor T cells (Ts) demonstrated that they possess determinants with antigen binding affinity and products of genes in the H-2 complex (MHC). Furthermore, antibodies against the variable region of Ig heavy chains or idiotypes have been shown to react with T-cell antigen receptors as well as antigen-specific helper and suppressor T-cell factors (TsF). It is, therefore, conceivable that at least two gene products are involved in the structural entity of these receptors: one each coded for by genes in either. To establish the molecular nature of the recognition component of T cells we have used homogeneous TsF from a T-cell hybridoma with a specific function. We report here that the antigen binding and I-J coded molecules on TsF are independently synthesised in the cytoplasm, and are secreted as an associated form of the two molecules; this association is required for antigen-specific suppression of antibody response.     

Hybrid hybridomas and their use in immunohistochemistry

A normal antibody-producing cell only expresses one antibody, resulting in the well-known phenomenon of allelic exclusion. When two myeloma cells are fused, the derived hybrids are capable of co-dominantly expressing the antibody genes of both parents. Although the respective variable (V) and constant (C) region genes remain expressed in the same cis configuration, heavy and light chains of both parents are scrambled, and hybrid molecules are formed. The same is true when a myeloma and an antibody-producing cell are fused to produce a hybrid myeloma (hybridoma). Fusion therefore allows the production of hybrid immunoglobulin molecules containing two different combining sites. Hybrid molecules of this type retain antigen-binding activity and specificity. Bispecific monoclonal antibodies secreted by hybridomas may have a variety of uses in biology and in medicine. Here we have focused on their application in histochemistry. As an example, we have prepared and tested an anti-somatostatin-anti-peroxidase bispecific antibody. This way of producing hybrid molecules is superior to the production of hybrid antibodies by chemical reconstitution methods because the drastic treatment required for chain separation in the latter is likely to lead to some protein denaturation and loss of antibody activity. Intracellularly synthesized and assembled hybrids do not suffer from this disadvantage. In addition, the recombination of heavy and light chains from different antibody molecules is likely to lead to considerable waste.     

Intraclonal generation of antibody mutants in germinal centres

The generation and selection of somatic antibody mutants are key elements of acquired immunity, essential for the affinity maturation of antibody responses dependent on T cells. The mutants are generated through a mechanism that introduces point mutations at high rate into rearranged variable (V) region genes in the course of cell proliferation. Their appearance coincides with the generation of germinal centres, which are characterized by oligoclonal B-cell proliferation and have been suggested to be the microenvironment in which antibody mutants are generated. We report here direct evidence for this hypothesis. Rearranged V-region genes were amplified from the genomic DNA of cells picked from individual germinal centres. The sequence analysis of these genes revealed that most represent cells of distinct B-cell clones which expanded locally, generating somatic antibody mutants at high rate. By contrast, antigen-induced proliferation of B cells at another site, periarteriolar lymphocyte sheath-associated foci, was not associated with somatic hypermutation.     

Localization of type 1 diabetes susceptibility to the MHC class I genes HLA-B and HLA-A

The major histocompatibility complex (MHC) on chromosome 6 is associated with susceptibility to more common diseases than any other region of the human genome, including almost all disorders classified as autoimmune. In type 1 diabetes the major genetic susceptibility determinants have been mapped to the MHC class II genes HLA-DQB1 and HLA-DRB1 (refs 1-3), but these genes cannot completely explain the association between type 1 diabetes and the MHC region. Owing to the region's extreme gene density, the multiplicity of disease-associated alleles, strong associations between alleles, limited genotyping capability, and inadequate statistical approaches and sample sizes, which, and how many, loci within the MHC determine susceptibility remains unclear. Here, in several large type 1 diabetes data sets, we analyse a combined total of 1,729 polymorphisms, and apply statistical methods-recursive partitioning and regression-to pinpoint disease susceptibility to the MHC class I genes HLA-B and HLA-A (risk ratios >1.5; P(combined) = 2.01 x 10(-19) and 2.35 x 10(-13), respectively) in addition to the established associations of the MHC class II genes. Other loci with smaller and/or rarer effects might also be involved, but to find these, future searches must take into account both the HLA class II and class I genes and use even larger samples. Taken together with previous studies, we conclude that MHC-class-I-mediated events, principally involving HLA-B*39, contribute to the aetiology of type 1 diabetes.     

Proteasome subunits encoded by the major histocompatibility complex are not essential for antigen presentation.

Major histocompatibility complex (MHC) class I molecules bind and deliver peptides derived from endogenously synthesized proteins to the cell surface for survey by cytotoxic T lymphocytes. It is believed that endogenous antigens are generally degraded in the cytosol, the resulting peptides being translocated into the endoplasmic reticulum where they bind to MHC class I molecules. Transporters containing an ATP-binding cassette encoded by the MHC class II region seem to be responsible for this transport. Genes coding for two subunits of the '20S' proteasome (a multicatalytic proteinase) have been found in the vicinity of the two transporter genes in the MHC class II region, indicating that the proteasome could be the unknown proteolytic entity in the cytosol involved in the generation of MHC class I-binding peptides. By introducing rat genes encoding the MHC-linked transporters into a human cell line lacking both transporter and proteasome subunit genes, we show here that the MHC-encoded proteasome subunit are not essential for stable MHC class I surface expression, or for processing and presentation of antigenic peptides from influenza virus and an intracellular protein.     

SB-restricted presentation of influenza and herpes simplex virus antigens to human T-lymphocyte clones

The HLA-D region of the human major histocompatibility complex (MHC) has been shown to be homologous to the murine I region in terms of both structure and function. Both regions encode class II MHC molecules which restrict T-lymphocyte interactions with antigen-presenting cells. We have recently described the MHC restriction and antigen specificities of human T-lymphocyte clones directed at strain A influenza virus. The majority of T-lymphocyte clones recognized antigen in the context of cell surface interaction products encoded by HLA-D/DR genes. However, a few clones recognized antigen presented by cells histoincompatible for D/DR antigens. We report here that some of these clones recognized viral antigens in association with antigens encoded by genes identical with or closely linked to the recently described secondary B-cell (SB) locus of the MHC. This is the first report that SB-restricted antigen recognition may form an integral part of normal, human immune responses.